Small paralax scroll problem

Hi

Ive a scroll script that I found somewhere which Ive been trying to adapt for my needs. I have one small problem however. The scroll reacts to the mouses position within the stage - I would however like it to only react within a small area in the screen (mcHit) I cant seem to get it working :frowning:

Ive posted my fla here http://www.contrastmedia.co.uk/downloads/test.fla

if anybody would be so kind as to help me with the problem. I think I know what the problem is but not how to fix it.

thanks for any help you can give

Nick