Selection List for External Table Entity

Hey guys,

I have a customer who wants to link to an external table to search for records. The external table has a customer number and that customer number is referenced by a customer table. They would like the search screen to show the list of customers in a drop down box as opposed to having to type in a customer number. When editing the Customer Number field on the external table I see that you can change it to a selection list but that's a manually populated list. Is there a way to do this thru the gui by building a search screen and using a runblock or do I need to create the search screen with a custom asp page and populate the selection list? If custom asp page does anyone have a sample of what that would look like. I would assume that i need to create another table connection to the customer table and then use FindRecord off of that entity to return all records and populate the selection list? Thanks for your help :-)