I don't understand what your problem is. You said that there were three front ends: A, B, and C. You also said there was a back end on a SQL server. So there shouldn't be ANY tables in any front end. The front ends are just for capturing data which are all stored -- whether captured in A, B, or C -- in ONE back end where all the tables are. If there is just one back end with tables, what exactly is your problem?
Michigan Dept. of Environmental Quality, Air Quality Division