Yes, you can. Assuming a very simple case first of your subject simply moving at a constant speed across the screen, you can position the zoomed in frame on the subject where he is at the beginning of the clip, then click the [End] button in the upper right corner of the pan/crop window and move the zoomed in frame to where the subject will be at the end of the clip. The frame will now follow the movement from the beginning to the end.

If the movement is more complex than that, you'll have to Split the clip every time the motion changes either direction or speed and set begin/end points for each clip. You'll want to copy the position values from the end of each clip to the beginning of the next to make sure you get smooth movement rather than having the frame instantly jump around at each split.

This sounds difficult, but it's actually rather easy once you've tried it a couple of times. It is rather time consuming though if you have to make lots of splits. Vegas allows you to set "keyframes" through the clip and smoothly move the frame around from place to place without having to split. If you're ever feeling in the mood to upgrade, this is one more reason to go for it.