Trying to add header using REUSE_ALV_COMMENTARY_WRITE', it is showing blank

Question

Hi,
I am trying to add header to my ALV grid report using the FM REUSE_ALV_COMMENTARY_WRITE'
It is displaying a blank window.
My code is
*& Report  YGTSPRODUCT
*& Author : Krishna Chaitanya Nandimandalam
*& Desc :   Display Products by Product Characteristics
REPORT  YGTSPRODUCT.
*& Structure declarations
type-pools : slis.
TYPES  : BEGIN OF TY_CTSNUMC,
         GUID_CTSNUMC TYPE /SAPSLL/CTSNUMC-GUID_CTSNUMC, "Primary Key as GUID in "RAW" Format
         GUID_MOBJ    TYPE /SAPSLL/CTSNUMC-GUID_MOBJ,    "Primary Key as GUID in "RAW" Format
         STCTS        TYPE /SAPSLL/CTSNUMC-STCTS,        "Numbering Scheme for Customs Tariff System
         CCNGN        TYPE /SAPSLL/CTSNUMC-CCNGN,        "Number (Generic/Structured)
         CRTSP        TYPE /SAPSLL/PRGEN-CRTSP,         "UTC Time Stamp When Object Was Added
         CHTSP        TYPE /SAPSLL/PRGEN-CHTSP,          "UTC Time Stamp When Object Was Changed
       END OF TY_CTSNUMC.
TEST --CREATING ANOTHER STUCTURE TO GET THE COMMON FIELD FOR GUID_PR
TYPES : BEGIN OF TY_PRCTSC,
        GUID_PRCTSC  TYPE /SAPSLL/PRCTSC-GUID_PRCTSC,   "Primary Key as GUID in "RAW" Format
        GUID_PR      TYPE /SAPSLL/PRCTSC-GUID_PR,  "Primary Key as GUID in "RAW" Format
        STCTS        TYPE /SAPSLL/PRCTSC-STCTS,   "Numbering Scheme for Customs Tariff System
        GUID_CTSNUMC TYPE /SAPSLL/PRCTSC-GUID_CTSNUMC, "Primary Key as GUID in "RAW" Format
        END OF TY_PRCTSC.
TYPES : BEGIN OF TY_PRGEN,
      GUID_PRGEN TYPE  /SAPSLL/PRGEN-GUID_PRGEN, "Primary Key as GUID in "RAW" Format
      GUID_PR    TYPE  /SAPSLL/PR-GUID_PR,       "Primary Key as GUID in "RAW" Format
      ATTR20A    TYPE  /SAPSLL/PRGEN-ATTR20A,    "Substance ID
      ATTR05A    TYPE  /SAPSLL/PRGEN-ATTR05A,    "Materail Type
      ATTR10A    TYPE  /SAPSLL/PRGEN-ATTR10A,    "Materail Group
      ATTR05B    TYPE  /SAPSLL/PRGEN-ATTR05B,    "Sub-Family
       END OF TY_PRGEN.
TYPES : BEGIN OF TY_PNTPR,
       GUID_PR TYPE /SAPSLL/PR-GUID_PR,
       PRVSY TYPE /SAPSLL/PNTPR-PRVSY,   "R3 MATERIAL NUMBER
       GRVSY TYPE /SAPSLL/PNTPR-GRVSY,   "LOGICAL SYSTEM GROUP
       END OF TY_PNTPR.
*TYPES : D_PSUI TYPE /SAPSLL/PRODUCT_SELECT_UI_S-QUAL_STA.  "PRODUCT STATUS
*TYPES : BEGIN OF D_CORSTA,
       GUID_MOBJ TYPE /SAPSLL/CORSTA-GUID_MOBJ,
       QUAL_STA TYPE /SAPSLL/CORSTA-QUAL_STA,
       CHTSP TYPE /SAPSLL/CORSTA-CHTSP,
       END OF D_CORSTA.
>PRODUCT STAUS
*DATA  : BEGIN OF T_CORSTA OCCURS 0,
       GUID_MOBJ TYPE /SAPSLL/CORSTA-GUID_MOBJ,
       QUAL_STA TYPE /SAPSLL/CORSTA-QUAL_STA,
       END OF T_CORSTA.
TYPES : BEGIN OF TY_PR,
        GUID_PR TYPE /SAPSLL/PR-GUID_PR,  "Primary Key as GUID in "RAW" Format
        CRTSP   TYPE /SAPSLL/PR-CRTSP, "PRODUCT CREATED ON
        CHTSP   TYPE /SAPSLL/PR-CHTSP, "PRODUCT CHANGED ON
        END OF TY_PR.
TYPES : BEGIN OF TY_PRT,
       GUID_PR TYPE /SAPSLL/PRT-GUID_PR, "Primary Key as GUID in "RAW" Format
       PRTXT   TYPE /SAPSLL/PRT-PRTXT,    "Materail description
        END OF TY_PRT.
TYPES : BEGIN OF TY_FINAL,
*T_PRCTSC
         GUID_PRCTSC  TYPE /SAPSLL/PRCTSC-GUID_PRCTSC,   "Primary Key as GUID in "RAW" Format
         GUID_PR      TYPE /SAPSLL/PRCTSC-GUID_PR,  "Primary Key as GUID in "RAW" Format
         STCTS        TYPE /SAPSLL/PRCTSC-STCTS,   "Numbering Scheme for Customs Tariff System
         GUID_CTSNUMC TYPE /SAPSLL/PRCTSC-GUID_CTSNUMC, "Primary Key as GUID in "RAW" Format
*T_CTSNUMC
        GUID_CTSNUMC TYPE /SAPSLL/CTSNUMC-GUID_CTSNUMC, "Primary Key as GUID in "RAW" Format
         GUID_MOBJ    TYPE /SAPSLL/CTSNUMC-GUID_MOBJ,    "Primary Key as GUID in "RAW" Format
        STCTS        TYPE /SAPSLL/CTSNUMC-STCTS,        "Numbering Scheme for Customs Tariff System
         CCNGN        TYPE /SAPSLL/CTSNUMC-CCNGN,        "Number (Generic/Structured)
        CRTSP        TYPE /SAPSLL/PRGEN-CRTSP,         "UTC Time Stamp When Object Was Added
        CHTSP        TYPE /SAPSLL/PRGEN-CHTSP,          "UTC Time Stamp When Object Was Changed
*T_PRGEN
         GUID_PRGEN TYPE  /SAPSLL/PRGEN-GUID_PRGEN, "Primary Key as GUID in "RAW" Format
        GUID_PR    TYPE  /SAPSLL/PR-GUID_PR,       "Primary Key as GUID in "RAW" Format
         ATTR20A    TYPE  /SAPSLL/PRGEN-ATTR20A,    "Substance ID
         ATTR05A    TYPE  /SAPSLL/PRGEN-ATTR05A,    "Materail Type
         ATTR10A    TYPE  /SAPSLL/PRGEN-ATTR10A,    "Materail Group
         ATTR05B    TYPE  /SAPSLL/PRGEN-ATTR05B,    "Sub-Family
*T_PNTPR
        GUID_PR    TYPE /SAPSLL/PR-GUID_PR,  "Primary Key as GUID in "RAW" Format
         PRVSY      TYPE /SAPSLL/PNTPR-PRVSY,   "R3 MATERIAL NUMBER
         GRVSY      TYPE /SAPSLL/PNTPR-GRVSY,   "LOGICAL SYSTEM GROUP
T_PR
       GUID_PR TYPE /SAPSLL/PR-GUID_PR,  "Primary Key as GUID in "RAW" Format
        CRTSP   TYPE /SAPSLL/PR-CRTSP, "PRODUCT CREATED ON
        CHTSP   TYPE /SAPSLL/PR-CHTSP, "PRODUCT CHANGED ON
*T_PRT
        GUID_PR TYPE /SAPSLL/PRT-GUID_PR, "Primary Key as GUID in "RAW" Format
         PRTXT   TYPE /SAPSLL/PRT-PRTXT,    "Materail description
        END OF TY_FINAL.
*& INTERNAL TABLE AND WORK AREA DECLARATIONS
DATA :
      T_CTSNUMC TYPE STANDARD TABLE OF TY_CTSNUMC INITIAL SIZE 0,
      T_PRCTSC   TYPE STANDARD TABLE OF TY_PRCTSC INITIAL SIZE 0, "TEST INCLUDED NEW STRUCTURE TO GET GUID_PR
      T_PRGEN TYPE STANDARD TABLE OF TY_PRGEN INITIAL SIZE 0,
      T_PNTPR TYPE STANDARD TABLE OF TY_PNTPR INITIAL SIZE 0,
      T_PR TYPE STANDARD TABLE OF TY_PR INITIAL SIZE 0,
      T_PRT TYPE STANDARD TABLE OF TY_PRT INITIAL SIZE 0,
     T_CORSTA TYPE STANDARD TABLE OF D_CORSTA INITIAL SIZE 0,
      T_FINAL TYPE STANDARD TABLE OF TY_FINAL INITIAL SIZE 0.
DATA :
       WA_CTSNUMC TYPE TY_CTSNUMC,
       WA_PRCTSC   TYPE TY_PRCTSC,   "TEST INCLUDED NEW STRUCTURE TO GET GUID_PR
       WA_PRGEN   TYPE TY_PRGEN,
       WA_PNTPR  TYPE TY_PNTPR,
       WA_PR TYPE TY_PR,
       WA_PRT TYPE TY_PRT,
      WA_CORSTA TYPE D_CORSTA,
       WA_FINAL TYPE TY_FINAL.
*& ALV DATA DECLARATIONS
DATA : lt_fieldcat TYPE slis_t_fieldcat_alv,
       lw_fieldcat LIKE LINE OF lt_fieldcat,
       lt_fieldcat1 TYPE slis_t_fieldcat_alv,
       lw_fieldcat1 LIKE LINE OF lt_fieldcat,
       lt_listheader TYPE slis_t_listheader,
       lw_listheader LIKE LINE OF lt_listheader,       lt_events TYPE slis_t_event,
       lw_events LIKE LINE OF lt_events.
*& DATA DECLARATIONS FOR SELECTION SCREEN
DATA : G_STCTS   TYPE /SAPSLL/CTSNUMC-STCTS, "NUMBER SCHEME
       G_ATTR20A TYPE /SAPSLL/PRGEN-ATTR20A, "SUBSTANCE ID
       G_PRVSY   TYPE /SAPSLL/PNTPR-PRVSY,   "R3 MATERIAL NUMBER
       G_GRVSY   TYPE /SAPSLL/PNTPR-GRVSY,   "LOGICAL SYS GROUP
     G_QSTA    TYPE /SAPSLL/PRODUCT_SELECT_UI_S-QUAL_STA, "PRODUCT STATUS
       G_CORSTA  TYPE /SAPSLL/CORSTA-QUAL_STA,  "PRODUCT STATUS
       G_CRTSP   TYPE /SAPSLL/PR-CRTSP,      "PRODUCT CREATED ON
       G_CHSTP   TYPE /SAPSLL/PR-CHTSP.      "PRODUCT CHANGED ON
*& SELECTION-SCREEN DECLARATIONS
SELECTION-SCREEN BEGIN OF BLOCK B1 WITH FRAME TITLE TEXT-001.
SELECT-OPTIONS : S_STCTS FOR G_STCTS OBLIGATORY,      "NUMBER SCHEME
                 S_AT20A FOR G_ATTR20A,    "SUBSTANCE ID
                 S_PRVSY FOR G_PRVSY,      "R3 MATERIAL NUMBER
                 S_GRVSY FOR G_GRVSY,      "LOGICAL SYS GROUP
                S_QSTA FOR G_QSTA,        "PRODUCT STATUS
                 S_CORSTA FOR G_CORSTA,    "PRODUCT STATUS
                 S_CRTSP FOR G_CRTSP,      "PRODUCT CREATED ON
                 S_CHSTP FOR G_CHSTP.      "PRODUCT CHANGED ON
SELECTION-SCREEN END OF BLOCK B1.
SELECTION-SCREEN BEGIN OF BLOCK B2 WITH FRAME. " TITLE. " TEXT-002.
PARAMETERS : BOTH  RADIOBUTTON GROUP RG1,
             EXICLASS RADIOBUTTON GROUP RG1.
SELECTION-SCREEN END OF BLOCK B2.
*& INITIALIZATION
INITIALIZATION .
  CLEAR : WA_CTSNUMC,
          WA_PRCTSC,
          WA_PRGEN,
          WA_PNTPR,
          WA_PR,
          WA_PRT,
          WA_FINAL.
  REFRESH : T_CTSNUMC,
            T_PRCTSC,
            T_PRGEN,
            T_PNTPR,
            T_PR,
            T_PRT,
            T_FINAL.
*&      START OF SELECTION
START-OF-SELECTION.
  LW_EVENTS-NAME = 'TOP_OF_PAGE' .
  LW_EVENTS-FORM = 'SUB' .
  APPEND LW_EVENTS TO LT_EVENTS .  PERFORM LIST_HEADER.
IF BOTH EQ 'X'.
  PERFORM VALIDATE_NSCHEME.
  PERFORM GET_DATA.
  PERFORM BUILD_FIELDCAT.
  PERFORM LIST_HEADER.
PERFORM f_events CHANGING lt_events.
  PERFORM DISP_ALV_DATA.
ENDIF.
*&      Form  VALIDATE_NSCHEME
*&            VALIDATE NUMBER SCHEME
FORM VALIDATE_NSCHEME .
  DATA : L_STCTS TYPE /SAPSLL/CTSNUMC-STCTS.
  SELECT SINGLE STCTS FROM /SAPSLL/CTSNUMC INTO L_STCTS
        WHERE STCTS IN S_STCTS .
  IF SY-SUBRC <> 0.
    MESSAGE 'Invalid Numbering Scheme for Customs Tariff System'
           TYPE 'E'.
  ENDIF .
ENDFORM.                    " VALIDATE_NSCHEME
*&      Form  GET_DATA
     GET DATA INTO FINAL TABLE
FORM GET_DATA .
  SELECT GUID_CTSNUMC "Primary Key as GUID in "RAW" Format
         GUID_MOBJ    "Primary Key of Main Object
         STCTS        "Numbering Scheme for Customs Tariff System
         CCNGN        "Number (Generic/Structured)
         CRTSP        "UTC Time Stamp When Object Was Added
         CHTSP        "UTC Time Stamp When Object Was Changed
         FROM /SAPSLL/CTSNUMC
         INTO TABLE T_CTSNUMC
         WHERE STCTS IN S_STCTS.
*DELETE ADJACENT DUPLICATES FROM T_CTSNUMC COMPARING GUID_CTSNUMC.
  IF T_CTSNUMC IS NOT INITIAL.
GET GUID_PR FOR THE CORRESPONDING GUID_CTSNUMC
    SELECT GUID_PRCTSC  "Primary Key as GUID in "RAW" Format
           GUID_PR      "Primary Key as GUID in "RAW" Format
           STCTS        "Numbering Scheme for Customs Tariff System
           GUID_CTSNUMC "Primary Key as GUID in "RAW" Format
           FROM /SAPSLL/PRCTSC
           INTO TABLE T_PRCTSC
           for all entries in t_ctsnumc
           WHERE GUID_CTSNUMC EQ T_CTSNUMC-GUID_CTSNUMC.
IF T_PRCTSC IS NOT INITIAL.
GET FIELDS FROM PRGEN BASED ON THE GUID_PR
    SELECT GUID_PRGEN "Primary Key as GUID in "RAW" Format
           GUID_PR    "Primary Key as GUID in "RAW" Format
           ATTR20A    "SUBSTANCE ID
           ATTR05A    "Materail Type
           ATTR10A    "Materail Group
           ATTR05B    "Sub-Family
           FROM /SAPSLL/PRGEN
           INTO TABLE T_PRGEN
           FOR ALL ENTRIES IN T_PRCTSC
           WHERE GUID_PR EQ T_PRCTSC-GUID_PR.
DELETE ADJACENT DUPLICATES FROM T_PRGEN COMPARING GUID_PR.
GET FIELDS FROM PNTPR BASED ON THE GUID_PR
    SELECT GUID_PR    "Primary Key as GUID in "RAW" Format
           PRVSY      "R3 MATERIAL NUMBER
           GRVSY      "LOGICAL SYSTEM GROUP
           FROM /SAPSLL/PNTPR
           INTO TABLE T_PNTPR
           FOR ALL ENTRIES IN T_PRCTSC
           WHERE GUID_PR EQ T_PRCTSC-GUID_PR.
*DELETE ADJACENT DUPLICATES FROM T_PRGEN COMPARING GUID_PR.
GET CORSTA-QUAL_STA FOR STATUS CATEGORY BESED ON THE T_CTSNUMC-GUID_MOBJ
*SELECT GUID_MOBJ
      QUAL_STA
      FROM /SAPSLL/CORSTA
      INTO TABLE T_CORSTA
      FOR ALL ENTRIES IN T_CTSNUMC
      WHERE GUID_MOBJ EQ T_CTSNUMC-GUID_MOBJ.
MISSING FIELD >>>>>>>PRODUCT STATUS
GET CRSTP CHSTP FROM PR BASED ON GUID_PR
    SELECT GUID_PR   "Primary Key as GUID in "RAW" Format
           CRTSP     "PRODUCT CREATED ON
           CHTSP     "PRODUCT CHANGED ON
           FROM /SAPSLL/PR
           INTO TABLE T_PR
           FOR ALL ENTRIES IN T_PRCTSC
           WHERE GUID_PR EQ T_PRCTSC-GUID_PR.
*DELETE ADJACENT DUPLICATES FROM T_PR COMPARING GUID_PR.
GET PRTXT FROM PRT BASED ON GUID_PR
    SELECT GUID_PR "Primary Key as GUID in "RAW" Format
           PRTXT   "MATERIAL DESCRIPTION
           FROM /SAPSLL/PRT
           INTO TABLE T_PRT
           FOR ALL ENTRIES IN T_PRCTSC
           WHERE GUID_PR EQ T_PRCTSC-GUID_PR.
*DELETE ADJACENT DUPLICATES FROM T_PRT COMPARING GUID_PR.
   ENDIF.
  ENDIF.
FILLING DATA INTO T_FINAL
REFRESH T_FINAL.
    LOOP AT T_PRCTSC INTO WA_PRCTSC.
      WA_FINAL-GUID_PRCTSC  = WA_PRCTSC-GUID_PRCTSC.
      WA_FINAL-GUID_PR      = WA_PRCTSC-GUID_PR.
      WA_FINAL-STCTS        = WA_PRCTSC-STCTS.
      WA_FINAL-GUID_CTSNUMC = WA_PRCTSC-GUID_CTSNUMC.
READ TABLE T_CTSNUMC INTO WA_CTSNUMC WITH KEY GUID_CTSNUMC = WA_PRCTSC-GUID_CTSNUMC.
IF SY-SUBRC = 0.
   WA_FINAL-GUID_CTSNUMC = WA_CTSNUMC-GUID_CTSNUMC.
     WA_FINAL-GUID_MOBJ    = WA_CTSNUMC-GUID_MOBJ.
   WA_FINAL-STCTS        = WA_CTSNUMC-STCTS.
     WA_FINAL-CCNGN        = WA_CTSNUMC-CCNGN.
   WA_FINAL-CRTSP        = WA_CTSNUMC-CRTSP.
   WA_FINAL-CHTSP        = WA_CTSNUMC-CHTSP.
ENDIF.
    READ TABLE T_PRGEN INTO WA_PRGEN WITH KEY GUID_PR = WA_PRCTSC-GUID_PR.
    IF SY-SUBRC = 0.
      WA_FINAL-GUID_PRGEN = WA_PRGEN-GUID_PRGEN.
      WA_FINAL-GUID_PR    = WA_PRGEN-GUID_PR.
      WA_FINAL-ATTR20A    = WA_PRGEN-ATTR20A.
      WA_FINAL-ATTR05A    = WA_PRGEN-ATTR05A.
      WA_FINAL-ATTR10A    = WA_PRGEN-ATTR10A.
      WA_FINAL-ATTR05B    = WA_PRGEN-ATTR05B.
    ENDIF.
    READ TABLE T_PNTPR INTO WA_PNTPR WITH KEY GUID_PR = WA_PRCTSC-GUID_PR.
    IF SY-SUBRC = 0.
     WA_FINAL-GUID_PR    = WA_PNTPR-GUID_PR.
      WA_FINAL-PRVSY      = WA_PNTPR-PRVSY.
      WA_FINAL-GRVSY      = WA_PNTPR-GRVSY.
    ENDIF.
    READ TABLE T_PR INTO WA_PR WITH KEY GUID_PR = WA_PRCTSC-GUID_PR.
    IF SY-SUBRC = 0.
     WA_FINAL-GUID_PR = WA_PR-GUID_PR.
      WA_FINAL-CRTSP   = WA_PR-CRTSP.
      WA_FINAL-CHTSP   = WA_PR-CHTSP.
    ENDIF.
    READ TABLE T_PRT INTO WA_PRT WITH KEY GUID_PR = WA_PRCTSC-GUID_PR.
    IF SY-SUBRC = 0.
     WA_FINAL-GUID_PR = WA_PRT-GUID_PR.
      WA_FINAL-PRTXT   = WA_PRT-PRTXT.
    ENDIF.
    APPEND WA_FINAL TO T_FINAL.
   DELETE ADJACENT DUPLICATES FROM T_FINAL COMPARING ATTR20A.
    CLEAR WA_FINAL.
  ENDLOOP.
ENDFORM.                    " GET_D
*&      Form  BUILD_FIELDCAT
      text
-->  p1        text
<--  p2        text
FORM BUILD_FIELDCAT .
REFRESH LT_FIELDCAT.
  lw_fieldcat-col_pos = 1.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'ATTR20A'.
  lw_fieldcat-seltext_m = 'SUBSTANCE ID'.
  lw_fieldcat-outputlen = '15'.
  lw_fieldcat-FIX_COLUMN = 'X'.
lw_fieldcat-KEY = 'X'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 2.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'PRVSY'.
  lw_fieldcat-seltext_m = 'R3 MAT NBR'.
  lw_fieldcat-outputlen = '14'.
  lw_fieldcat-FIX_COLUMN = 'X'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 3.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'PRTXT'.
  lw_fieldcat-seltext_m = 'MAT DESCRIPTION'.
  lw_fieldcat-outputlen = '19'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 4.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'GRVSY'.
  lw_fieldcat-seltext_m = 'LOGICAL SYS GRP'.
  lw_fieldcat-outputlen = '21'.
  APPEND lw_fieldcat TO lt_fieldcat.
lw_fieldcat-col_pos = 5.
lw_fieldcat-tabname = 'T_FINAL'.
lw_fieldcat-fieldname = 'QUAL_STA'.
lw_fieldcat-seltext_m = 'PRODUCT STATUS'.
  lw_fieldcat-outputlen = 'x'.
APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 6.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'CRTSP'.
  lw_fieldcat-seltext_m = 'PRODUCT CREATED ON'.
  lw_fieldcat-outputlen = '21'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 7.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'CHTSP'.
  lw_fieldcat-seltext_m = 'PRODUCT CHANGED ON'.
  lw_fieldcat-outputlen = '21'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 8.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'ATTR05A'.
  lw_fieldcat-seltext_m = 'MATERIAL TYPE'.
  lw_fieldcat-outputlen = '18'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 9.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'ATTR10A'.
  lw_fieldcat-seltext_m = 'MATERIAL GRP'.
  lw_fieldcat-outputlen = '18'.
  APPEND lw_fieldcat TO lt_fieldcat.
  lw_fieldcat-col_pos = 10.
  lw_fieldcat-tabname = 'T_FINAL'.
  lw_fieldcat-fieldname = 'ATTR05B'.
  lw_fieldcat-seltext_m = 'SUB-FAMILY'.
  lw_fieldcat-outputlen = '18'.
  APPEND lw_fieldcat TO lt_fieldcat.
lw_fieldcat-col_pos = 11.
lw_fieldcat-tabname = 'T_FINAL'.
lw_fieldcat-fieldname = 'CCNGN'.
lw_fieldcat-seltext_m = 'SUBID CLASSIFICATION'.
APPEND lw_fieldcat TO lt_fieldcat.
lw_fieldcat-col_pos = 12.
lw_fieldcat-tabname = 'T_FINAL'.
lw_fieldcat-fieldname = 'CCNGN'.
lw_fieldcat-seltext_m = 'SUBID CLASSIFICATION'.
APPEND lw_fieldcat TO lt_fieldcat.
lw_fieldcat-col_pos = 13.
lw_fieldcat-tabname = 'T_FINAL'.
lw_fieldcat-fieldname = 'CCNGN'.
lw_fieldcat-seltext_m = 'SUBID CLASSIFICATION'.
APPEND lw_fieldcat TO lt_fieldcat.
CLEAR LW_FIELDCAT.
ENDFORM.                    " BUILD_FIELDCAT
*&      Form  LIST_HEADER
      text
-->  p1        text
<--  p2        text
FORM LIST_HEADER .
DATA :  LT_LISTHEADER TYPE slis_t_listheader,
        LW_LISTHEADER LIKE LINE OF lt_listheader.
  LW_LISTHEADER-TYP = 'H'.
  LW_LISTHEADER-INFO = 'DISPLAY PRODUCTS BY PRODUCT CHARACTERISTIC'.
  APPEND LW_LISTHEADER TO LT_LISTHEADER.
  LW_LISTHEADER-TYP = 'S' .
  LW_LISTHEADER-KEY = 'TIME' .
  LW_LISTHEADER-INFO = SY-UZEIT .
  APPEND LW_LISTHEADER TO LT_LISTHEADER.
  LW_LISTHEADER-TYP = 'S' .
  LW_LISTHEADER-KEY = 'DATE' .
  LW_LISTHEADER-INFO = SY-DATUM .
  APPEND LW_LISTHEADER TO LT_LISTHEADER.
  LW_LISTHEADER-TYP = 'S' .
  LW_LISTHEADER-KEY = 'CLIENT' .
  LW_LISTHEADER-INFO = SY-MANDT .
  APPEND LW_LISTHEADER TO LT_LISTHEADER.
ENDFORM.                    " LIST_HEADER
*&      Form  DISP_ALV_DATA
      text
-->  p1        text
<--  p2        text
FORM DISP_ALV_DATA .
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
  I_BUFFER_ACTIVE                   = ' '
    I_CALLBACK_PROGRAM                = 'I_REPID'
  I_CALLBACK_TOP_OF_PAGE            = 'TOP-OF-PAGE1'
  I_STRUCTURE_NAME                  =
  I_BACKGROUND_ID                   = ' '
   I_GRID_TITLE                      = 'GTS Substance- Product Classification Report'.
  I_GRID_SETTINGS                   =
  IS_LAYOUT                         =
    IT_FIELDCAT                       = LT_FIELDCAT
  IT_EXCLUDING                      =
  IT_SPECIAL_GROUPS                 =
  IT_SORT                           =
  IT_FILTER                         =
  IS_SEL_HIDE                       =
  I_DEFAULT                         = 'X'
  I_SAVE                            = ' '
  IS_VARIANT                        =
    IT_EVENTS                         = LT_EVENTS
IMPORTING
  E_EXIT_CAUSED_BY_CALLER           =
  ES_EXIT_CAUSED_BY_USER            =
  TABLES
    T_OUTTAB                          = T_FINAL
EXCEPTIONS
  PROGRAM_ERROR                     = 1
  OTHERS                            = 2
IF SY-SUBRC <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
        WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
ENDFORM.                    " DISP_ALV_DATA
FORM SUB.
CALL FUNCTION 'REUSE_ALV_COMMENTARY_WRITE'
  EXPORTING
    IT_LIST_COMMENTARY       = LT_LISTHEADER.
  I_LOGO                   =*
  I_END_OF_LIST_GRID       =*
  I_ALV_FORM               =*
ENDFORM.
Any suggestions and help will be appreciated!
Regards,
Kittu

Answer 1

Hi Ram,
When I had put a Break point on the FM Reuse_alv_grid_display
The parameter IT_EVENTS is not getting populated and it is not calling the FORM SUB.
But LT_EVENTS is holding the data 'TOP_OF_PAGE' and the form name as SUB.
FORM DISP_ALV_DATA .
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
  I_BUFFER_ACTIVE                   = ' '
    I_CALLBACK_PROGRAM                = 'I_REPID'
  I_CALLBACK_TOP_OF_PAGE            = 'TOP-OF-PAGE1'
  I_STRUCTURE_NAME                  =
  I_BACKGROUND_ID                   = ' '
   I_GRID_TITLE                      = 'GTS Substance- Product Classification Report'.
  I_GRID_SETTINGS                   =
  IS_LAYOUT                         =
    IT_FIELDCAT                       = LT_FIELDCAT
  IT_EXCLUDING                      =
  IT_SPECIAL_GROUPS                 =
  IT_SORT                           =
  IT_FILTER                         =
  IS_SEL_HIDE                       =
  I_DEFAULT                         = 'X'
  I_SAVE                            = ' '
  IS_VARIANT                        =
    IT_EVENTS                         = LT_EVENTS
IMPORTING
  E_EXIT_CAUSED_BY_CALLER           =
  ES_EXIT_CAUSED_BY_USER            =
  TABLES
    T_OUTTAB                          = T_FINAL
EXCEPTIONS
  PROGRAM_ERROR                     = 1
  OTHERS                            = 2
IF SY-SUBRC <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
        WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
ENDFORM.                    " DISP_ALV_DATA
FORM SUB.
CALL FUNCTION 'REUSE_ALV_COMMENTARY_WRITE'
  EXPORTING
    IT_LIST_COMMENTARY       = LT_LISTHEADER.
  I_LOGO                   =
  I_END_OF_LIST_GRID       =
  I_ALV_FORM               =
ENDFORM.
Any suggestions will be apprectiated.
Regards,
Kittu