Creating A Drop Down List For Names And Addresses ...

I'm writing a purchase order entry form for my company. I've used the above formulas to create drop down lists with addresses for each of our stores and vendors, but I need form to automatically select the correct "ship to:" location. Some stores will always have merchandise shipped to the store regardless of the vendor. Other stores will always have the product shipped to a warehouse location, but in a few stores the product will be shipped either to the store or a warehouse depending on the vendor.

I've been able to work out the formulas for the stores that have shipments always to one location by creating a second address table and linking the selected store to it.

Here is basically what I need:

Store A + Vendor A = Store A
Store A + Vendor B = Store A
Store B + Vendor A = Warehouse
Store B + Vendor B = Store B
Store C + Vendor A = Warehouse
Store C + Vendor B = Warehouse