>Is my only option to inform users that this isn't possible due to bad database design?

If you don't have any control over the data design, then perhaps you could post a better example of what your data structures are. From your first post it wasn't clear how the tables were related or what the uCode (IIRC) was for. If you could post something that creates the structures (just the fields that are important) like the little example I posted, that would be great.