Creating an Elastic Line

I’ve been searching Google and this site for tutorials for this and can’t find anything which seems to fit what I’m looking for. I’m trying to divide the screen in 2 and then allow user to rollover the middle of screen - when they do, depending which direction they drag, the bottom or top of the screen bulges and then springs back into place. I’ve created this mock-up:

http://www.idigitdesign.com/testarea/flash/

Wherever the user rolls over which the mouse, that is where the line bulges.

I have tried this tutorial:
http://www.kirupa.com/developer/actionscript/spring.htm

but I can’t figure out how to get from a single ball to a solid block which bulges at different points depending on where the mouse action is.

I really can’t figure this one out so any help or ideas would be much appreciated.

Thanks all.