Help with Complex Button please

Hi,
im currently trying to use this script to create a little thumnail gallery:
http://www.kirupa.com/developer/mx2004/button_effect.htm

first off my main flash file has 2 movie clips in, an empty on which an image will be loaded into and one with a navigation menu on.
now within the navigation there is a button which will load an external swf into that same movie clip.

This loaded swf contains the “Complex Button”

my problem is that i dont know how to (or if it is possible) to use these buttons to load a jpg into the empty movie clip on the main timeline
im guessing it has something to do with:

this.onRelease  =  function(){

getURL("http://www.kirupa.com","_blank");

}

but i have tried a couple of things and havent been able to work it out as im still a bit of a n00b with actionscript

Any help would be very much appreciated and sorry if i didnt explain myself very well
thanks