Problems with Thumbnail scrolling

I’ve recently done the following tutorial:

and I’ve managed to get it all working and change the look of etc to match thesite I need it for.

The problem is I dont want to have to copy and paste those frames into my own flash file. I tried creating a movie clip with them in instead and it all works apart from the slider bar. I’m guessing its because the hit_left and hit_right movieclips are now within another movie clip and so aren’t registering when the mouse is over them…

What other way can I get this to work?

Many Thanks in advance