Load in external swf on click - button

help please

was so easy in AS2 but seem really complicated in AS3, doh!

would someone please help?? I am trying to simply load in an external swf when I click a button. I have created a button on the stage called it ‘my_button’

I can get the swf to load in automatically but I am not understanding the script for loading it in on a click…would someone pleae explain what script I need to have : (

this is the script I have for loading automatically

var loader_mc : Loader = new Loader();
var urlRequest : URLRequest = new URLRequest("photography.swf");
loader_mc.load(urlRequest);
addChild(loader_mc);

works great just would like to have it load in on a button click, can someone help

aaaarrrgghhhh!!!