Stephen,
Forgive me for not fully understanding, but are you suggesting that the data source - the .DBF(s) will change with each running of the report? This is pretty standard. If it's just a single table that's in different locations but always the same structure, then just open it with the same ALIAS <name> each time. If it's mutiple tables then just do an SQL SELECT into a cursor that uses what ever tables you need, so that the REPORT file (.FRX) always sees the same data "view". (You could also use a View, but they are a bit more difficult to create "on-the-fly".)
OR, do wish to alter the format of the REPORT file (.FRX) itself, to allow different fields to be displayed or with different groupings? This too can be done, although it's a bit more complicated, and you'll need to dig into the specifications (both documented and un-documented) for how this file is used by the internal VFP REPORT code.
Rick