Catching the MouseUp of a TScrollBox

In Delphi 6, I'm using a TScrollBox to show a bunch of panels which display information, the panels are arranged in rows and columns.

I need to perform certain actions after every change of the TScrollbox's scrollbar's position.

My question is: How do I capture that event?  My first guess was to use the mouse events on the TScrollbox, but that doesn't work.

Something tells me I'm not the first person to ask this question

Thanks,
Kirk