Fission will let you do this, but it's $32:
Rogue Amoeba - Fission: Lossless Audio Editor for Mac OS X
Rogue Amoeba's software is generally well worth the money, mind you.
Not sure it will do WMV, though.
Other possibility: In iTunes, get Info on the trance mix and in the Options, set start and end points to the beginning and end of the piece you want to extract (I believe accuracy is down to 0.01 seconds). Then, select that track and go to "Advanced" --> "Convert selection to <whatever your import settings are in iTunes' preferences>" and it will RE-rip that piece and add it to your iTunes library, where you can edit the tag info.
You'll need to do this for every piece in the mix that you want to extract, but it's free. AFAIK, it also re-encodes to mp3 a second time, so you possibly lose some quality, as well.