Please help with a pan and zoom file!

Hopefully someone will be able to help me with this file. I found a cool flash file online that allows the view to pan and zoom with the mouse. For my own uses, I modified it somewhat, adding buttons that triggered pop up windows, changed out the graphic, and also the zooming increments.

However, I have not been able to figure out how to keep the panning feature constrained by the boundaries of my graphic, which is going to be an aerial map. I want to limit the boundaries to the dimensions of the actual map, so the viewer does not continue to pan beyond the graphic, if that makes any sense. I am uploading a revised copy of the fla, I swapped out the bitmap graphics with generic vector shapes making it look more generic. If anyone can figure this out, I would really really appreciate it!