Preloading external images

1

Okay, i found this AS on a site for prealoading external images.


stop();
//stage
Stage.showMenu = false;
Stage.scaleMode = "noScale";

MovieClip.prototype.preloadjpg = function(movietobeLoaded) {
	var holder = this.createEmptyMovieClip("holder", 1);
	holder.loadMovie(movietobeLoaded);
	this.onEnterFrame = function() {
		holder._visible = false;
		var tLoaded, tBytes;
		tLoaded = holder.getBytesLoaded();
		tBytes = holder.getBytesTotal();
		var percentage = int(tLoaded * 100 / tBytes);
		info_txt.text = percentage + " % of " + movietobeLoaded + " loaded";
		if (isNaN(tBytes) || tBytes < 4) {
			return;
		}
		if (tLoaded / tBytes >= 1) {
			
			placeholder_mc.loadMovie(movietobeLoaded);
			info_txt.text = movietobeLoaded + " is loaded & displayed";
			delete this.onEnterFrame;
		}
	};
};

this.placeholder_mc._x = this.placeholder_mc._y = 0;

I’m not really sure how to use it…
Questions:

How can i load images into that preloader using buttons? i’m not really sure how it works in general, I’m not completely AS illiterate, i’m just confused about this, also is it possibl to load them into mcs i already have on the stage, instead of using the AS declared place holder mc?

If anyone has time, an example .fla would be greatly apprciated…if not, an explanation would help…