Personlizing a check box on Oracle professional form

Hi

We are required to use personalization to make an Encumbrance  Reserve check box checked by default when the purchase order is auto created.

Currently it is manually reserved.

have done the following, but it is not working

Condition:

Trigger event:   WHEN-NEW-BLOCK-INSTANCE

Trigger Object: PO_HEADERS

Condition: :PO_HEADERS.STATUS = 'Incomplete'

Action:

Object Type: Item

Target Object: PO_APPROVE.RESERVE

Property Name: VALUE

Value: TRUE

Please see attached screen shots for further clarity.

Regards