[SD] Check Payment term in VA01/VA02 (FORM USEREXIT_SAVE_DOCUMENT_PREPARE)

[PURPOSE] 
Check whether the payment term is suitable for the customer or not in VA01/VA02.

[TOOL] 
INCLUDE: MV45AFZZ
USEREXIT: USEREXIT_SAVE_DOCUMENT_PREPARE

XVBAK ← New data if any change/else it will be same as old
YVBAK ← Old value
VBAK ← Work area

when you deal with Items it will be some thing like this..
XVBAP ← New data if any change/else it will be same as old
YVBAP ← Old data if any change(considers item) /else it is blank

If we want to get SO header where in header or items, we can obtain from WA: VBAK does not concerned to use XVBAK or YVBAK or OVBAK.

[CODE]

FORM USEREXIT_SAVE_DOCUMENT_PREPARE.

  DATA: P_ZTERM TYPE KNB1-ZTERM,
               P_MESSAGE TYPE STRING.

** GET PAYMENT TERM IN CUSTOMER MASTER DATA
  CLEAR P_ZTERM.
  SELECT SINGLE ZTERM INTO P_ZTERM FROM KNVV WHERE KUNNR = VBAK-KUNNR
                                               AND VKORG = VBAK-VKORG
                                               AND VTWEG = VBAK-VTWEG
                                               AND SPART = VBAK-SPART.

** CHECK ITEM PAYMENT TERM
  LOOP AT XVBKD WHERE POSNR <> '000000'.
  CHECK XVBKD-ZTERM <> P_ZTERM.
  CONCATENATE 'ITEM' XVBKD-POSNR 'PAYMENT TERM WON'T BE' XVBKD-ZTERM ',PLEASE CHOOSE' P_ZTERM '!' INTO P_MESSAGE.
  ENDLOOP.

** CHECK HEADER PAYMENT TERM
  READ TABLE XVBKD WITH KEY POSNR = '000000'.
  IF XVBKD-ZTERM <> P_ZTERM.
  CONCATENATE XVBAK-KUNNR 'PAYMENT TERM WOULD BE' P_ZTERM ',CHECK PLEASE!' INTO P_MESSAGE.
  ENDIF.

  CHECK P_MESSAGE <> ' '.
  MESSAGE E001(00) WITH P_MESSAGE.
  FCODE = 'ENT1'.

ENDFORM.