Flexible progres barr - Please Help!

I’m learning flash on my own.
I use this code, and it working well. This is external .swf preloader for the “01.jpg” - width 600 pix.

but
the “01.pg” will be changed dynamic in future, so I need to make progerss bar which will fit to different size (width) of images.

//Frame 3 script

this.createEmptyMovieClip(“MyExternallyLoadedSWFMovieHolder”,0);
var MyVariable = “01.jpg”;
MyExternallyLoadedSWFMovieHolder._x = 0;
MyExternallyLoadedSWFMovieHolder._y = 0;

//Preloader script

total_bytes = (this._parent.MyExternallyLoadedSWFMovieHolder.getBytesTotal());
loaded_bytes = (this._parent.MyExternallyLoadedSWFMovieHolder.getBytesLoaded());
remaining_bytes = (total_bytes-loaded_bytes);
percent_done = (int((loaded_bytes/total_bytes)*600));
bar.ba.target = (percent_done);
DisplayProgress = (Math.round(bar.ba._width))+" % loaded.";
if (bar.ba._width>599) {
gotoAndPlay(4);
} else {
gotoAndPlay(2);
}

Any suggestions?

Thanx