Restriction Ctl+F11 on Purchase Order form

Hi,

At present, users are able to view all purchase order on purchase order form. As per requirement users should not view all PO's hence I made form personalization on PO summary form and working( it will disable OPEN button) but on Purchase Order form they are able to view using F11 and querying required PO.

Eg: PO Number -123, should not view by user-1. He is able not able to view on purchase order summary due to form personalization but able to view on Purchase order form using F11. How can I restrict F11 for specific PO's / users using form personalization or is able to achieve this functionality apart from form personalization.