Alv sort error ?

Question

hi friends ı write this code .
data : BEGIN OF g_itable OCCURS 0,
       COLOR LIKE icon-id, "emrah color degisken
       bukrs LIKE bkpf-bukrs,
       belnr LIKE bkpf-belnr,
       gjahr LIKE bkpf-gjahr,
       koart LIKE bseg-koart,
       koart_text(60) TYPE c,
       dmbtr LIKE bseg-dmbtr,
       dmbtr1 LIKE bseg-dmbtr,
       name1 LIKE kna1-name1,
       buzei LIKE bseg-buzei,
       shkzg LIKE bseg-shkzg,
       kunnr LIKE bseg-kunnr,
       budat LIKE bkpf-budat,
       header_th(100) TYPE n,
       hkont LIKE bseg-hkont,
       lifnr LIKE bseg-lifnr,
END OF g_itable.
  PERFORM FILL_T_SORT
       USING  : 'G_ITABLE' 'HEADER_TH' 'X' '' ''.
FORM FILL_T_SORT USING   TABNAME FIELDNAME UP DOWN SUBTOT .
  CLEAR U_SORT .
  MOVE : TABNAME   TO U_SORT-TABNAME   ,
         FIELDNAME TO U_SORT-FIELDNAME ,
         UP        TO U_SORT-UP        ,
         DOWN      TO U_SORT-DOWN      ,
         SUBTOT    TO U_SORT-SUBTOT    .
  APPEND U_SORT .
ENDFORM.  
  CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
   EXPORTING
  I_INTERFACE_CHECK                 = ' '
  I_BYPASSING_BUFFER                =
  I_BUFFER_ACTIVE                   =
     I_CALLBACK_PROGRAM                = gd_repid
   I_CALLBACK_PF_STATUS_SET          = 'GUI'
     I_CALLBACK_USER_COMMAND           = 'COMMAND'
     I_CALLBACK_TOP_OF_PAGE            = 'TOP_OF_PAGE'
  I_CALLBACK_HTML_TOP_OF_PAGE       = ' '
  I_CALLBACK_HTML_END_OF_LIST       = ' '
  I_STRUCTURE_NAME                  =
  I_BACKGROUND_ID                   = 'DTY_BACKGROUND'
  I_GRID_TITLE                      =
  I_GRID_SETTINGS                   =
     IS_LAYOUT                     = gd_layout
     IT_FIELDCAT                  = fieldcatalog[]
  IT_EXCLUDING                      =
  IT_SPECIAL_GROUPS_LVC             =
  IT_SORT_LVC                       =
  IT_FILTER_LVC                     =
  IT_HYPERLINK                      =
  IS_SEL_HIDE                       =
  I_DEFAULT                         = 'X'
   I_SAVE                            = 'A'
      IS_VARIANT               = VARIANTE
  IT_EVENTS                         =
  IT_EVENT_EXIT                     =
  IS_PRINT_LVC                      =
  IS_REPREP_ID_LVC                  =
  I_SCREEN_START_COLUMN             = 0
  I_SCREEN_START_LINE               = 0
  I_SCREEN_END_COLUMN               = 0
  I_SCREEN_END_LINE                 = 0
  I_HTML_HEIGHT_TOP                 =
  I_HTML_HEIGHT_END                 =
  IT_ALV_GRAPHICS                   =
  IT_EXCEPT_QINFO_LVC               =
    IT_SORT                  = U_SORT[]
  IR_SALV_FULLSCREEN_ADAPTER        =
IMPORTING
  E_EXIT_CAUSED_BY_CALLER           =
  ES_EXIT_CAUSED_BY_USER            =
    TABLES
      t_outtab                          = g_itable2
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.
where do ı do error?help me please

Answer 1

probably you have to specify field SPOS in your UT_SORT.