Ease : pixels instead of _y

1

hi people

i’m using the following code to ease mc’s

 
MovieClip.prototype.easingY = function(toY){
 this.onEnterFrame = function(){
 this._y -= (this._y-toY)/3;
 if(this._y > toY-4 && this._y < toY+4){
 this._y = toY;
 delete this.onEnterFrame 
 } } }

now i have to provide a Y position to move to…is it possible to change this code so that instead of providing a Y position i give it a amount of pixels to move (up/down)? ex. move 100 pixels UP from current y or move 222 pixels down…

thanks