Limit the available PO that users can receive against

We are on EBS 11.5.10

We have an issue where  people receive deliveries against somebodyelse PO(purchase orders) , sometimes the PO amount and items are the same (we have not achieved 100% central purchasing)

I have a requirement to only show certain PO's to receivers,so they can only receive on the displayed PO in the LOV (list of values)  we have not concluded on what parameters to limit the available PO's in the LOV , i think it will probably be driven by department

I am thinking of doing this in the custom.pll for the receipt form, but i want to get some other perspectives and see which is the best alternative any input is greatly appreciated