Forms :: Using Merge Statement In 6i?

in Toad I am using this Merge statement , working accordingly.I want to use this merge statement in my form where can I use it.

I created a Procedure in Form Named Proc_merge and call it when validate item of :bankcode

PROCEDURE proc_merge IS
BEGIN
declare
v_com varchar2(5000);
BEGIN
V_COM := '

[code]...

when matched then

update set
trg.v_chq = src.cheque_no, trg.v_bankcode = src.bank_code ,trg.v_debit=src.debit, trg.v_credit=src.credit, trg.v_narration=src.narration

when not matched then

insert (trg.v_type, trg.v_no, trg.v_date, trg.v_chq, trg.v_bankcode, trg.v_debit, trg.v_credit, trg.v_narration)
values (src.voucher_type, src.voucher_no, src.voucher_date, src.cheque_no, src.bank_code, src.debit, src.credit, src.narration)
';
FORMS_DDL(V_COM);
end;
END;

no any result.