Avoid duplicates in detail-block

Question

I have a master-detail form, the detail block have item, qty & rate. only 1 item_code is allowed to b entered per invoice, purchased at different rates. what i want to acheive is;
1) prevent user from entering duplicate item-code, if the detail record goes more then 1. and in case if there r more than 1 detail-record, then the new item-code shud appear the same as the item-code entered in the previous record.
B4 incorporating the above rule, i had already entered some records, thus manually taking into consideration the above rule. Later, when i tried to code the abov rule, m getting err-msg as per my triggers. what i did actually for this is;
i created a control-field m_item_code in control_block(Ctrl). NOT initialised anywhere.
then for the detail-block m using these triggers;
WHEN-REMOVE-RECORD
:dtl_blk.item_CODE = :ctrl.m_ITEM_code
WHEN-NEW-RECORD-INSTANCE
:dtl_blk.item_CODE = :ctrl.m_ITEM_code
for the field item_code triggers;
WHEN-VALIDATE-ITEM
DECLARE
     CURSOR C_ITEM IS SELECT ITEM_desc
     FROM item_MAST
     WHERE ITEM_code = :dtl_blk.item_CODE;
BEGIN
     IF :SYSTEM.CURSOR_VALUE IS NOT NULL AND
          :CTRL.M_item_CODE = :dtl_blk.item_CODE THEN
               OPEN C_ITEM;
               FETCH C_ITEM INTO :CTRL.M_ITEM_DESC;
               IF C_ITEM%NOTFOUND THEN
                    MESSAGE('ITEM does not exists!');
                    MESSAGE(' ');
                    RAISE FORM_TRIGGER_FAILURE;
               END IF;
               CLOSE C_ITEM;
     ELSE
               MESSAGE('Blank NOT allowed and NO different Item can be entered');
               MESSAGE(' ');
               RAISE FORM_TRIGGER_FAILURE;
     END IF;
END;
POST-TEXT-ITEM
:ctrl.m_item_code := :det_blk.item_code;
for the OLD RECORDs (those i entered b4 writing the above triggers), the rule works fine when i query, with whatever i have coded. BUT the problem is now for the NEW detail_RECORDS. as i enter in the detail block & give value in the first item-code field the err-msg ('Blank NOT allowed and NO different Item can be entered') in WVI above, flashes for the item-code. i dont know what i have done for this rule till now is corrct?
kindly give ur comments & guide me please for the more accurate & complete approach for my rule. kindly do tell where n which code to b used or crrected

Answer 1

Hi
You can achieve this by the use of PLSQL table create one small package in that defined your table and procdure, when user move to new record insert old record should be insert into the PLSQL table. select the value from PLSQL table to validate the next record. the ITEM_CODE must be delete from PLSQL table when user delete any ITEM_CODE from the block.