How to delete unneeded files from prior torrent version?

I'm moving some of my torrents over to a ultra.cc seedbox. When I download a revised torrent, it checks the files and only downloads what new files are needed. The new torrent may also have files which are not needed anymore, and need to be removed.

On my desktop client, I would simply move the torrent directory to a different folder on the same drive, and that would leave the unnecessary files behind for a quick cleanup. Is there a way to accomplish the same thing on ultra.cc? I'm using their r(u)torrent interface.