One way might be to have your CMS rename the file every hour, and update the link on where ever u have it.
So for example, if its blah.flv.... store that in ur db then on the hour have a script 1 rename the file, then 2 update the html to reflect the proper path/file name.
Technically someone coujld hot link your flv for like 1 hour max BUT, maybe u could do something with that