How to link to an audio file using the first 5 characters

I have an asp search results page listing available audio files. The files all have unique names excepting for the first 5 characters which are numbers above 10,000, i.e.:

37014 - Noah and the Flood.mp3
26185 - Life of Abraham.mp3
...
etc.

I have an objRst("ID") field that contains the sermon number (The first 5 numbers). I am trying to figure out how to create a link using the ID field that points to the audio file. I think it should be something like: File like Left(filename, 5) but I can't figure out how to make it work

Any suggestions?

TIA,

Jim
...