Using Garage band to rip audio

I've got a quicktime dvd of a concert from which I want to rip the audio to listen to on my ipod. I've gotten the movie into itunes and have "added markers" at the various points, but when I import the audio into itunes it just goes as one big track. Could someone please tell me, step by step, how to get a quicktime into garage band (I've got that part), divide the audio into tracks, and then import these tracks (as distinct ones) into itunes?

Many thanks!