Purchase Order Problem

Question

HI Experts,
  I have copied a purchase order form ZMEDRUCK from Medruck.  Modified according to the requirements of functional consultant without deleting a single element.  I have commented everything in the windows except /E - element lines.  Used subroutines to fetch some data and displayed.  Its working normally, but when enduser is trying to generate a PO with some JPY currency, it is not giving print preview nor print. 
In the subroutine pool for calculating grand total I have used the following code.
FORM freight TABLES   TA_INPUT STRUCTURE ITCSY
                        TA_OUTPUT STRUCTURE ITCSY.      "Structure
  DATA: TP_FREIGHT LIKE KONV-KAWRT,  " freight charges
        TP_CUSTOMS LIKE KONV-KAWRT,  " customs charges
        TP_EBELN   LIKE EKKO-EBELN,  " PO number
        TP_KNUMV   LIKE EKKO-KNUMV,  " document condition number
        TP_GTOTAL  TYPE P DECIMALS 2,  " grand total
        TP_TOTAL   LIKE KONV-KAWRT. " like konv-kawrt  " total before freight and customs.
  DATA: lv_grandtot(16),             " TYPE P DECIMALS 2,
                                   " lv_grandtot type konv-kawrt,
        tp_total1(16),
        tp_waers like ekko-waers.
  DATA : IT_KONV LIKE KONV OCCURS 0 WITH HEADER LINE. " for condition values.
  read table TA_INPUT with key 'EKKO-EBELN'.
  TP_EBELN = TA_INPUT-VALUE.
  CALL FUNCTION 'CONVERSION_EXIT_ALPHA_INPUT'
    EXPORTING
      INPUT  = TP_EBELN
    IMPORTING
      OUTPUT = TP_EBELN.
  READ TABLE TA_INPUT WITH KEY 'KOMK-FKWRT'.
**without this function module, getting short dump while adding for grand total.
**CONDENSE TA_INPUT-VALUE.
*MOVE TA_INPUT-VALUE TO TP_TOTAL.
  CALL FUNCTION 'CATS_ITS_MAKE_STRING_NUMERICAL'
    EXPORTING
      INPUT_STRING  = TA_INPUT-VALUE
    IMPORTING
      VALUE         = TP_TOTAL
    EXCEPTIONS
      NOT_NUMERICAL = 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.
READ TABLE TA_INPUT WITH KEY 'EKKO-WAERS'.
tp_waers = ta_input-value.
if tp_waers = 'JPY'.
tp_total = tp_total * 10.
endif.
WRITE: TP_TOTAL TO TP_TOTAL1 CURRENCY 'JPY' LEFT-JUSTIFIED.
  SELECT SINGLE KNUMV FROM EKKO INTO TP_KNUMV WHERE EBELN = tp_ebeln.
  SELECT * FROM KONV INTO TABLE IT_KONV WHERE KNUMV = TP_KNUMV
                                      AND KSCHL IN ('FRB1' , 'ZOB1').
*BREAK-POINT.
  LOOP AT IT_KONV.
    CASE IT_KONV-KSCHL.
      WHEN 'FRB1'.
        TP_FREIGHT = TP_FREIGHT + IT_KONV-KBETR.
      WHEN 'ZOB1'.
        TP_CUSTOMS = TP_CUSTOMS + IT_KONV-KBETR.
    ENDCASE.
  ENDLOOP.
*******grand total.
***here if don't use function module CATS_ITS_MAKE_STRING_NUMERICAL, I get short dump.
  TP_GTOTAL = TP_TOTAL + TP_FREIGHT + TP_CUSTOMS.
*WRITE TP_GTOTAL TO lv_grandtot CURRENCY tp_waers DECIMALS 2 LEFT-JUSTIFIED.
WRITE TP_GTOTAL TO lv_grandtot CURRENCY tp_waers LEFT-JUSTIFIED.
*move tp_gtotal to lv_grandtot.
  loop at TA_OUTPUT.
    case TA_OUTPUT-NAME.
      when 'TP_FREIGHT'.
        MOVE TP_FREIGHT TO TA_OUTPUT-VALUE  .
        CONDENSE TA_OUTPUT-VALUE.
        modify TA_OUTPUT.
      when 'TP_CUSTOMS'.
        MOVE TP_CUSTOMS TO TA_OUTPUT-VALUE  .
        CONDENSE TA_OUTPUT-VALUE.
        modify TA_OUTPUT.
      when 'TP_GTOTAL'.
        MOVE lv_grandtot TO TA_OUTPUT-VALUE  .
        CONDENSE TA_OUTPUT-VALUE.
        modify TA_OUTPUT.
    endcase.
  endloop.
endform.                    "freight
It is working well even with JPY currency, but this time when she was entering a material with JPY currency, neither preview is coming nor print.  In the status bar(in me21n) it shows error that a certain include is not available, but when I enter into script debugging mode, print preview is coming and grand total is 0, because of error in function module.  In the ABAP debugging mode, in the function module I have used, the sy-subrc is 1.  This is go-live issue and this problem has occurred in Prod server.  We could not stimulate the scene in Dev server.
In Dev, I noticed that when ever I tick off in 'Ret PO' check box, the same problem is coming.
Can any one help me with this problem.

Answer 1

The table PO_AGENTS stores the buyers .
To define a buyer, you need to define an employee (Purchasing super user > Setup > Personnel > Employees), then a Buyer (Purchasing super user > Setup>Personnel > Buyers)