[flexcoders] Display only part of a canvas??

[jmfillman]

I have a Canvas that with a height of 3000. For some users, I only want 
them to be able to view and scroll a portion of the height of the 
canvas, say 1200-2200. It can vary from user to user, and some will 
need to see the entire height. I'm at a loss as to whether or not this 
is even possible, and if so, how.