Update a table from Form's Check Box wise

BEGIN
GO_BLOCK ('data_block_1');
FIRST_RECORD;
LOOP
UPDATE stscinfd
SET precls = :crq2.s_present
WHERE precls = :crq2.s_previous
and studid=:data1.studid
and nvl(:data1.s_fail,'Y') <> 'N';
IF SQL%NOTFOUND THEN
null;
END IF;

EXIT WHEN :SYSTEM.LAST_RECORD = 'TRUE';

NEXT_RECORD;
END LOOP;
COMMIT;
clear_form;
END;