Automatic Value populate in DFF attributes

Hi All,

I am want to do Form Personlization on AP Invoice DFF attributes.

Requirement:

I want to populate attribute value automatically with SUM of Amount Remaining of supplier when the time of standard invoice booking.

Ex:

I have select Supplier Name: XXC from LOV then Tab out , now i want to see "SUM of Amount Remaining of supplier" automatically

I have tried but no luck

Condtion Tab:

=============

Trigget Event: WHEN-NEW-RECORD-INSTANCE

Trigger Object: INV_SUM_FOLDER

Actions Tab:

=============

Type: Built_In

Built In Type: Execute PROCEDURE

Argument

  ='declare

begin

update ap_invoices_all

set attribute5='''||${ITEM.PAYMENT_SCHEDULE.AMOUNT_REMAINING.VALUE}||'''