ActionScript 2.0 :: F8 - Slowing / Stopping Movement At Two Set Extremes

Using Flash 8 - AS2. I have a movie clip that moves from side to side based on the position of the mouse. If the mouse is right of center, the movie clip moves left, the speed based on the distance of the pointer to the center. Conversely, the same for the other direction.

Here's the AS on the clip event:
PHP Code:
onClipEvent(load){
speed=10;
}onClipEvent(enterFrame){
this._x += (_root.center-_root._xmouse)/speed;
}
(the speed variable is just a simple method to slow down my motion.)

Now what I need it to do and can't figure out out is this:
> How to get it to have upper and lower limits of motion.
> How to get it to slow down and stop at the upper and lower limits
> How to get it to stop at the limit until the mouse triggers movement back in the other direction

Logically, it could be said in this manner:
1) Move the clip right or left based on mouse position.
2) If clip _x nears the maximum (or minimum), change speed as a function of the distance remaining to the extent - in order to slow down the movement.
3) When clip _x reaches the maximum (or minimum), stop motion and permit no further motion in that direction.