var loader:MovieClipLoader = new MovieClipLoader();
var listener:Object = new Object();
listener.onLoadStart = function(target:MovieClip):Void {
	target._visible = false;
	target._alpha = 0;
};
listener.onLoadInit = function(target:MovieClip):Void {
	target._visible = true;
	target.onEnterFrame = function():Void {
		this._alpha += 5;
		if (this._alpha >= 100) {
			this._alpha = 100;
			delete this.onEnterFrame;
		}
	};
};
loader.addListener(listener);

btn.onRelease = function():Void {
	loader.loadClip("sample.jpg", mc);
};