To avoid duplicate entries in multi row

Question

Hi i need to avoid duplicate entries in multi record form.In the master block i have AGENCY CODE.These are the fields, RATING_CODE(composite primary key alng with AGENCY_CODE in the detail block,but set as hidden) and DESCRIPTION
in the detail block.If AGENCY_CODE is CRISIL,then for that i should not enter duplicate RATING CODES.I have written
DECLARE
     L_COUNT2 NUMBER;
     l_ret varchar2(20);
BEGIN
     SELECT COUNT(*) INTO L_COUNT2 FROM CSTM_AGENCY_CODE_DETAIL
WHERE AGENCY_CODE=:BLK_CSTM_AGENCY_CODE_DETAIL.AGENCY_CODE
AND RATING_CODE=:BLK_CSTM_AGENCY_CODE_DETAIL.RATING_CODE;
IF L_COUNT2 > 0 THEN
          l_ret := ovpkcs.fn_dispmsg('AGYCOD-03;',';',';');
Raise Form_Trigger_Failure;
END IF;
END;
in WHEN_VALIDATE_ITEM.
Now when i press the TAB to move next time it gives the message,DUPLICATE RATING CODE.The
problem is when i move back to the previous record by clicking mouse and change it to the already existing value,and while i save the validation is not happening and the message is not shown.Kindly tell me where i should code.
Thank you

Answer 1

hy,
you can check whan commit( an save button)
for i = 1 to n-1
check condition (item = item +1)
next_record
end
or by stored insert whit exception return to form program when duplicate key is found
...