A conditional value list based on a relationship is possible as you can relate a table to itself. This is called a "self join" relationship.
But there's a simpler way and you've almost go it.
If you want a value list drawn from the name field, but that excludes names from records where Inactive = "yes", use this calculation field as the source of names in your value list set up:
If ( IsEmpty ( Inactive ) ; Namefield )
Note that when there is no 'else' specified a null value is returned so drawing names from this calculation field does exactly what you need here.
Here are some links on conditional value lists. Note that the method I show here is referred to as "option 1" in the first link:
Forum Tutorial: Custom Value List?
Knowledgebase article: http://help.filemaker.com/app/answers/detail/a_id/5833/kw/conditional%20value%20list
Hierarchical Conditional Value lists: Conditional Value List Question
Feel free to post follow up questions here if those links aren't enough to get your value lists working correctly.
Wow! A million thanks. If ( IsEmpty ( Inactive ) ; Namefield ) is exatly what I was looking for. I simply made a new field in my Salesperson table that was a calculation field, dropped that in and tweaked it to match my field names exactly. The other thread would have also worked, thanks. (not sure how I missed that, I guess I was using the wrong keywords in my search)