Flash Drag and Limit

I need some help with coding to drag an MC across the stage but limit it from going off the stage. I was able to limit it so it only moves along the x-axis, but I need the mc to stop when it gets to the end. I also am not sure of how I would drag or scroll around the stage once I have zoomed in. As you can see, the limit I set on the y-axis has not prevented me from going anywhere once I am zoomed in. Please see the file at http://yourdesignateddesigner.com. And also, if anyone knows how to stop the mc from jumping when you drag it, that would be great too.

Here’s the code I used to limit the y-axis movement:

wall_mc.onPress = function() {
var dragging = false;
this.onEnterFrame = function() {
//stop dragging move mc to limit and drag again
if ((wall_mc.limit2._y+wall_mc._y)<=400) {
//botomm
stopDrag();
wall_mc._y = 400-wall_mc.limit2._y;
startDrag(this);
}
if ((wall_mc.limit1._y+wall_mc._y)>=0) {
// superior
stopDrag();
wall_mc._y = 0;
startDrag(this);
}