Forms Personalization in Miscellaneous Transactions form

 Good afternoon,

I am trying to create a forms personalization. Requirements is as follows.

"Give warning if the Transaction Type is 'Misc. receipt - DPLE' and there is value in the Descriptive Flexfield Attribute1.

The Trigger event is WHEN-NEW-ITEM-INSTANCE

and the Trigger is MTL_TRX_LINE.ATTRIBUTE3

The condition is

:MTL_TRX_HEADER.TRANSACTION_TYPE_NAME='Misc. receipt - DPLE'
AND
:MTL_TRX_LINE.ATTRIBUTE1 IS NULL

The Action Type is Message

The message type is Warning

The warning message is Project number is required in Descriptive Flexfield. "

When i perform the transaction with the above values it does not return the warning. In this form WHEN-NEW-ITEM-INSTANCE trigger event does not work.