[plt-scheme] Draggable panel divider?

Hi,

I'd like to be able to create a window with two panels which can be resized
using a "draggable panel divider", similar to the divider between the
Interactions and Definitions panels in the main DrScheme window. Has anyone
implemented something like this which can be easily reused, such as a
subclass of panel% ?

I suppose the code is there somewhere in the DrScheme IDE code, but I
couldn't find it. Pointers to where the code is would also be helpful.

thanks,
Alex