Help! won't stop scrolling

I have a textbox set up which is being masked. Then two buttons to scroll the text up and down. I actually wanted the buttons to be movieclips, but I settled because mc’s weren’t working…anyway…

The issue I’m looking to get resolved: As you scroll down, the text won’t stop scrolling when it gets to the end (and as you scroll up, it goes higher than where the text begins).

I tried using .scroll property, but that doesn’t seem to be working. For example, I tried on the down btn:

on (release) {
abouthitsville.scroll = abouthitsville.scroll - 1;

I’ve attached the current files I’m working with, so you all can see the AS.