I've figured out how to use track motion to get a PIP but when I do it affects the entire track and not just the single event. Please help me correct this problem.
Track motion always effects the entire track, hence the name "track" motion rather than "event" motion. Of course, you can use keyframes in versions 6 & 7 to vary the motion from one point to the next.
Pan/Crop lets you do a PIP effect one event at a time, rather than the whole track.