ftp question

I have an FTP server that I want to allow people to upload/download files. My server uses Unix permissions and I set the folder to have write and execute access. This way the users will have to know the name of the file to retreive it. The problem is, how can I as an administrator delete old files? I'm using WS FTP Pro. The files aren't listed (of course) and I figured hitting 'delete' on the remote directory would prompt me to type the file name the same way it does when I attempt to download a file but it doesn't. I'm using a hosting service so I can't give specific user id's specific access which makes this difficult.