You can either use different algorithm for deciding when to add new file (*),
or just use single database file (what platform do you use ?).

(*) It is better to have at least one additional secondary file,
otherwise you could miss the right point for adding next file
when using 2GB files. E.g. if you have files
db.fbd, db.fb2, db.fb3
you can add new file (db.fb4) when FB starts to fill the file db.fb3.


Ivan
http://www.volny.cz/iprenosil/interbase