creating a drop down list for names and addresses

Thanks to all the people who posted in this thread, your info allowed me to create my drop down lists with addresses. However I need to find out how to go one step further.
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


Is there any way to do this?

I don't think I was clear. I'm not looking to display and actual '+' sign, but more like an "if 'a' and 'b' then 'c'" The user will select a value (e.g. store location) from the drop down list in say cell a1 and select another value (e.g. vendor) from another drop down list in cell b2. The form will generate a value (e.g. shipping location) in a 3rd cell.
If what you posted will do that, then I am confused about the formula you posted.

Here's a example of what I need. I hope the upload works