Using proftpd, is there a good way to automatically synchronise uploaded files from the upload directory to some other directory?

Our layout ends up a bit like this:

~/ftp/some/path <-- Files are uploaded here
~/some/other/path/not/accessible/via/ftp <-- But also need to be here after uploading

Is there a good way to do this automatically, or do I have to tell anyone uploading files to upload twice, and open up an additional directory (containing data we cannot redistribute)?