That's what "use values from field" value lists are primarily used for. With such a value list, you can specify __pkVendorID as the first field and you can select CompanyName as the second field. This allows you to select a company by name, but the value list enters the corresponding ID number when you make a selection.
There's a step by step illustrated description of how to set this up in "Adventures in FileMaking #1 - conditional value lists". You are not setting up conditional value list here, but if you click the button for "Basic Conditional Value Lists", you can then click a button named "Defining Field Based Value Lists" to get to this detailed step by step description.
Phil, Thank you! I'm still trying to get my head around these concepts, but this put me on the right track!
Note that while this works, it has limitations. It's a good starting point, but the limitations--which can become pretty painful when the list of values becomes large often lead to replacing this set up with more sophisticated options. I've started something called "Adventures in FileMaking" that are database files that sort of function like interactive e-zines on specific subjects. The first two issues address ways to improve on the "use values from field" value list tool:
They are free to download.
Adventures in FileMaking #1 - Conditional Value Lists (includes details on how to set up a basic field based value list)
Adventures in FileMaking #2 - Enhanced Value Selection (what to do when a simple value list won't cut it.)