se hai Flash Player 7:

codice:
MovieClip.prototype.slowSetProperty = function(prop, newVal, b) {
	var bb, prevVal;
	bb = (b == undefined) ? 5 : b;
	var prevVal = this[prop];
	if (this["slowSPController"+prop] != undefined) {
		this["slowSPController"+prop].removeMovieClip();
	}
	this.createEmptyMovieClip("slowSPController"+prop, this.getNextHighestDepth());
	this["slowSPController"+prop].onEnterFrame = function() {
		this._parent[prop] += (newVal-this._parent[prop])/bb;
		if (Math.abs(this._parent[prop]-prevVal)<.01) {
			this._parent[prop] = newVal;
			this.removeMovieClip();
		} else {
			prevVal = this._parent[prop];
		}
	};
};

esempio:

codice:
clip.slowSetProperty("_x",50);
il terzo parametro è opzionale e serve a regolare la velocità.