The typical technique for doing what you're needing involves using filtered value lists and global fields. See previous thread on the subject at:
I will have a more indepth look at that thread later.
OK Mke , I have had a look at the thread you sent and I will explain myself clearer.
As the user selects a value from a fixed list ie B01, B02....B15 ect, the selection made drops off the value list so as not to be selected again (from the same reducing value list) for that particular group.
I hope this is clearer.
You want "Dwindling Value Lists". see a demo here
It says FM8-11, but if you are using fm12, the technique should still work.
Search for "filemaker dwindling valuelists" in your favorite search engine to see other methods.