Just a thought: does your FTP-program keep a daily log with names of uploaded files?

If so, can you not just delete all files mentioned in the log which was created 30 days ago?

You might want to check if the same file (or at least a file with the same name) was not uploaded later, so you can reset the timer.

Dumping the log-file into a database shouldn't be too difficult and a simple SQL-query will give you a nice list of files to be deleted.

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law