Isn't there a bpm counter in logic? I'm sure it's in the logic plugins under helper. If you import a piece of audio in to logic and play it the bpm counter will tell u the speed. Obviously this will only work with tracks with a strong consistent beat. But once u know the speed of the track things may be easier. TRUST ME THIS THING YOU WANT TO DO IS MUCH EASIER IN ABLETON LIVE! I KNOW I DJ WITH IT!