Assign a file on the server to the audio field of FFPC

I already have a ton of MP3s uploaded to my server, and I have switched to drupal as my CMS. I've used CCK to build a form to upload other information about the MP3s (title, speaker, notes), but I really don't want to have to upload the audio again just to get the audio associated with the node. How can I associate an existing MP3 on the server with the audio field of a CCK form?

I know PHP and MySQL, so if someone just told me where this info is put in the database, that would be awesome.

Thanks,

Richard