3 Tracks as in one track with 3 songs on it?
If so I would cut the track into the 3 songs. Then you could export each song into a new GB file, or if you want them in the same file, move each song to a new track. Then you have to do 3 separate exports to iTunes, each time muting two tracks and having one track audible. I don't think there is a way to send 3 different songs into itunes from the same GB file.
I'm not sure if I was able to answer your question, post back with any more questions.
goodluck