How to repeatedly overlay image in Canon EOS Utility?

So, I have a Canon Rebel T1i, and love using it's Live View feature on my laptop for stop motion animation. But, to onion skin the previous image, I have only been able to load one image at a time, and I have to navigate to that file after EVERY shot. In EOS Utility (on Mac for me) is there a way to have it automatically load the last shot taken?