On Purchase Order Entry, option to only show Stock Items with chosen Supplier set against the Item

Currently, when entering a new Purchase Order in Sage it is possible to select any Stock Item for any Supplier regardless of whether that Supplier is set up against the Stock Item. For some customers it would be useful to only be able to select Stock Items on new Purchase Orders where the Supplier is set up against the Stock Item. Perhaps this could be a tick option in POP Settings.