Purchase Order Lock

It would be nice to be able to "lock" a PO and prevent any orders from attaching to said PO. There are times when we do large booking orders for stock with vendors and those PO's aren't scheduled to ship for 2-6 months. I have to go and remove these orders from the long term PO, so I can raise a PO that will ship ASAP.

This causes problems when we don't notice that an ASAP order has attached to a long term PO.