Hi Anuj,
In the table control, in PAI event there must be LOOP which is validating field inputs using CHAIN ENDCHAIN.
There you will get a module names as
MODULE tbc_9001_modify ON CHAIN-REQUEST.
In this module , check the condition and write the code as :
MODIFY i_tab
FROM wa_tab
INDEX tbc_9001-current_line.
Code to be added :
IF SY-SUBRC NE 0 and wa_tab is not initial.
APPEND wa_tab to I_tab.
ENDIF.
Hope it helps...
Thanks,
Sumit