[plt-scheme] How to detect mouse movements?

I am working on my final project for my basic programing class. I want
to know how to use the on-mouse-event feature. I tried loading up the
teachpack world and I tried adding the on-mouse-move into my code. I
basically want to detect the location of the mouse when it is moved on
top of a canvas from the teach pack draw.  Can you give me an example
of how to use the mouse event commands? Thanks.