Building PO's from Requisition lines

Greetings,

Our finance department doesn't want Requisitions that haven't been fully approved to be able to be selected in the 'Copy From' area when creating a PO. Currently, if one line is approved, they can select that one line to build into a PO.

My question: Is there a setting that I'm missing to define the criteria for Requisition selection? Or is the only solution to modify the search function on the page  PO_REQ_SOURCE?

Thanks in advance for any advice!

Eric