Hi Terry!

I went ahead and added a movable divider (also known as a "sash") using the PanedWindow widget. http://effbot.org/tkinterbook/panedwindow.htm#reference

I also converted the master window to use a grid geometry manager. It looks like you can use pack manager and grid managers together as long as each manager is separated by a container/frame. So I use the pack manager to manage the scrollbars within the Frame. It ended up working out nicely.

I've attached a patch and would like to submit it for review!