The getUrl() method is for opening other web addresses, as in getUrl( "http:google.com" ). It works just like a hyper link in HTML. If I understand your question, it seems that you want to load a swf into the existing swf and call methods on it. In that case, you should use the MovieClipLoader. The following is pseudo-code but should get you close.
var loadListener:Object = new Object();
loadListener.onLoadComplete = function(target_mc:MovieClip, httpStatus:Number):Void
{
trace( "onLoadComplete" );
trace( "loaded content: " + target.getInstanceAtDepth(0) );
}
var mcLoader:MovieClipLoader = new MovieClipLoader();
mcLoader.addListener( loadListener );
var mc:MovieClip = this.createEmptyMovieClip( "mc", this.getNextHighestDepth() );
mcLoader.loadClip( "nameOfTheSwfYouWantToLoad.swf", mc);