Ability to select a project + Project Item on purchase order requisition

If project accounting available + integrated, user should be able to select a project + project item for a PO Requisition line. This will be passed to the Purchase Order when generated. Problem = user requests PO's for goods, but these need to be assigned to a project. The authoriser has no knowledge of which project + will need to talk to the requesting user to be able to assign a project after the generation stage.