Inventory Bin Table which could be turned on or off in Company Maint.
Off would allow "Free Form" typing into the Bin Location (current method).
On would reference a "Base Table" of possible locations. Any place where "Bin Location" is, there would now be a Drop Down List of locations to choose from, disallowing any Free Form typing, just clicking.
This way someone doesn't type Shelf 1 today and Shelf-1 tomorrow, thus creating an entirely new Bin Location & making a Physical Inventory Count a nightmare.