Regular changes to an htaccess redirect

I have a site that hosts a monthly podcast and on most pages there is an audio player that plays the latest episode.

I have it set to play latest.mp3 and .ogg and hoped to use an htaccess redirect every time a new episode comes out to redirect it to the correct new audio file.

Problem is, certainly in Firefox anyway, it seems as if the browser is caching the redirect info. Is there a better way of doing this?

I guess I could duplicate the audio files and rename them latest.mp3 and .ogg but I assume that I'd have the same problem if the browser caches the audio file.

Any clues?

Thanks

Richard