Scrollbar troubles

For reference - (ignore the bad photoshopped labels as they were for another question)

Okay i’m trying to get a customisable scroll-bar to work. Which in itself shouldn’t be hard but i’m finding rather illogical. The scrollbar is in the bottom left.

I have a movie clip with a group of buttons i want to scroll down, but they will not stop. When they reach the top point of the movie clip the scrolling will stop, but when i go to scroll down, it goes on forever.

How i have it set up is i have a layer with the movie clip, which is masked to hide the parts i don’t want to see. I have two seperate buttons on a layer, which respectively run up and down and move the movie clip appropriately. The scrollbar is supposed to move within these boundaries but it won’t correspond with the buttons when i use them. When i click on it to drag it doesn’t work, it just makes things disappear within the movie clip.

What i am using is this code on a seperate layer to run it -

scrolling = function () {
var scrollHeight:Number = scrollTrack._height;
var contentHeight:Number = contentMain._height;
var scrollFaceHeight:Number = scrollFace._height;
var maskHeight:Number = maskedView._height;
var initPosition:Number = scrollFace._y=scrollTrack._y;
var initContentPos:Number = contentMain._y;
var finalContentPos:Number = maskHeight-contentHeight+initContentPos;
var left:Number = scrollTrack._x;
var top:Number = scrollTrack._y;
var right:Number = scrollTrack._x;
var bottom:Number = scrollTrack._height-scrollFaceHeight+scrollTrack._y;
var dy:Number = 0;
var speed:Number = 10;
var moveVal:Number = (contentHeight-maskHeight)/(scrollHeight-scrollFaceHeight);

scrollFace.onPress = function() {
var currPos:Number = this._y;
startDrag(this, false, left, top, right, bottom);
this.onMouseMove = function() {
dy = Math.abs(initPosition-this._y);
contentMain._y = Math.round(dy*-1*moveVal+initContentPos);
};
};
scrollFace.onMouseUp = function() {
stopDrag();
delete this.onMouseMove;
};
btnUp.onPress = function() {
this.onEnterFrame = function() {
if (contentMain._y+speed<maskedView._y) {
if (scrollFace._y<=top) {
scrollFace._y = top;
} else {
scrollFace._y -= speed/moveVal;
}
contentMain._y += speed;
} else {
scrollFace._y = top;
contentMain._y = maskedView._y;
delete this.onEnterFrame;
}
};
};
btnUp.onDragOut = function() {
delete this.onEnterFrame;
};
btnUp.onRollOut = function() {
delete this.onEnterFrame;
};
btnDown.onPress = function() {
this.onEnterFrame = function() {
if (contentMain._y-speed>finalContentPos) {
if (scrollFace._y>=bottom) {
scrollFace._y = bottom;
} else {
scrollFace._y += speed/moveVal;
}
contentMain._y -= speed;
} else {
scrollFace._y = bottom;
contentMain._y = finalContentPos;
delete this.onEnterFrame;
}
};
};
btnDown.onRelease = function() {
delete this.onEnterFrame;
};
btnDown.onDragOut = function() {
delete this.onEnterFrame;
};

if (contentHeight<maskHeight) {
scrollFace._visible = false;
btnUp.enabled = false;
btnDown.enabled = false;
} else {
scrollFace._visible = true;
btnUp.enabled = true;
btnDown.enabled = true;
}
};
scrolling();

But it doesn’t seem to work. Any flash handy people know whats going on? Thanks.