In the user exit EXIT_SAPLIEDP_902 I have added the below code for PAYEXT IDOC -
LOOP AT edidd_table WHERE segnam = 'E1IDKU3'.
CLEAR ls_e1idku3.
ls_e1idku3 = edidd_table-sdata.
IF ls_e1idku3-paiuzawe = 'B'.
ls_e1idku3-paiuzawe = 'R'.
ENDIF.
edidd_table-sdata = ls_e1idku3.
MODIFY edidd_table.
ENDLOOP.
But the idoc segment data is not changing , can anyone please help?