Seting boundries when moving mc with ._x values

K heres my deal. I’m moving this little red box along the x axis. It just moves w/ the mouse but it moves off the movie clip area, i want to be able to set the left and right boundries. Heres my code. Any help would be great.

[color=red]mc_movingBox.onEnterFrame = function() {
var xMouse = _root._xmouse;
if(Math.abs(xMouse - this._x) < 1) {
this._x = xMouse;
} else {
this._x -= (this._x-xMouse) / 6;