Oracle Forms

hello to all,
i m making a form on which i placed a push button and write the following trigger when-button-pressed trigger :-
declare
d date:=to_date(sysdate,'yyyymm');
d1 varchar2(6):=to_char(d,'yyyymm');
cursor c is select * from prmamed where empno=00000127 and earningdeduction='E0010';
begin
set_application_property(cursor_style,'busy');
for rec in c loop
update prmamed
set paycalperiod=d1;
exit when c%notfound;
next_record;
end loop;
commit;
Message('updation done');
message(' ');
set_application_property(cursor_style,'default');
end;
but when i m pressing this push button then i m getting this error:-
frm-40735 when-button-pressed trigger raised unhandled exception ora-01858
plz help me out in removing this error
and could i use EXTRACT keywork to get the current year and month for the updation.