Payables Invoice woprkbench customization

Hi,

I want to customize invoice work bench so user cannot enter invoice in closed period.

But when I created customization on when-validate-record it is working but when query records it fires there also , is there any other event for this?

My code is this

:INV_SUM_FOLDER.INVOICE_DATE not between

(SELECT to_date(min(start_date),'DD-MON-RRRR')

FROM GL_PERIOD_STATUSES_V

WHERE APPLICATION_ID = '200' AND SET_OF_BOOKS_ID = 1

AND NVL(ADJUSTMENT_PERIOD_FLAG, 'N') = 'N' 

and closing_status='O')

and

(SELECT to_date(max(end_date),'DD-MON-RRRR')

FROM GL_PERIOD_STATUSES_V

WHERE APPLICATION_ID = '200' AND SET_OF_BOOKS_ID = 1