Forms :: How To Drop And Create Constraints With Forms_ddl

forms_ddl('ALTER TABLE ACCOUNT.VOC_DETAIL DROP CONSTRAINT FK_VOC_NO');
forms_ddl('ALTER TABLE ACCOUNT.VOC_MASTER DROP CONSTRAINT PK_VOC_MASTER');

forms_ddl('ALTER TABLE ACCOUNT.VOC_MASTER ADD CONSTRAINTS PK_VOC_MASTER primary key(VOC_NO)');
forms_ddl('ALTER TABLE ACCOUNT.VOC_DETAIL ADD CONSTRAINTS FK_VOC_NO FOREIGN KEY(VOC_NO) REFERENCES VOC_MASTER(VOC_NO)');

the trigger works very well but when i add some trigger between drop and create constraints then first step drop constraint sucessfully but 2nd trigger when create new constraints not working examples of trigger are as under:-

declare
s_number varchar2(7);
cursor masters is
select voc_type,voc_date,voc_no from account.voc_masterorder by voc_type,voc_date,voc_no;
abc masters%rowtype;
cursor detail is
select voc_no,ref_no from account.voc_detail group by voc_no,ref_no;
[code]....