Actionscript fade mc

1

This works great for fadding a mc in but does anyone know how to switch it to fade that same mc out for a mid frame transition?

THANKS!

MovieClip.prototype.Increment = function(maxAlpha, speed) {
this.onEnterFrame = function() {
this._alpha += speed;
if (this._alpha>=maxAlpha) {
this._alpha = maxAlpha;
delete this.onEnterFrame;
}
};
};
with (clip) {
_alpha = 0;
Increment(100, 15);
}