Well.. if you know how to program hard-and-software you could do this...
But this would be very, very difficult..
Like how are you gonna tell your computer knows what cd 3 is.. (which playlist is cd#3).
Sorry to say, but I think you'd be better of with a 'normal' mp3-setup as we use here. This means that you need an AUX-input on your headunit. (or an FM-Transmitter)
Go ahead and read some off the old posts.
Also have a look at www.mp3car.com/searchexamples.asp
and look what the other guys in here have created..