expiring mp3 files

We are searching for a programmer that can create for us a simple api or program to be able to do what the public library do with the audio books that are rented online, that is make them expirable after a certain datel. In other words, for the mp3 file to work and play no matter if it was downloaded onto another device, but after certain date of downloading it, for it to stop working or not play. According to a blog I read in creative cow. com it can be done like this... • Access the date/time info on ANY given computer • At the first play, run an internal routine that will calculate a value from the date/time info and then modify itself to store that calculated value • On subsequent plays, access the time/date info again and then run a different internal routine to compare it to the stored value. • Following the previous comparison, execute yet a third internal routine, an IF-THEN-ELSE command: IF the just-accessed value for date and time is equal to or greater than the stored value, THEN destroy the file... or ELSE do nothing to the file If that is not correct, What is really important is for it to do what we need to do with our mp3 files.