Loading SWF's one on top of the other

So this is my first time posting here and I am still a newbie so please bear with me. I’ve been on other forums and I can’t seem to get a clear answer to what I need. So forgive me if I seem a little too meticulous with my question here. I just want to be as clear as possible. …and anyone that can help me figure this out … I’m buyin’ lunch!

OK, so I need to copy an effect that you will see on this site:
http://www.stratocucine.com

I have a row of buttons on my main stage. Each button will load a different external SWF. Each SWF contains an image and an animated mask that moves from top to bottom slowly revealing the image. When a button is clicked a SWF loads onto the main stage and an image is revealed from top to bottom. Now, I know that if I want to achieve the effect of one image scrolling OVER the other & not IN PLACE OF ( in other words I still want to see the previous image underneath as the second image scrolls over it), I need to assign each SWF to a differnt level. This, of course works fine. However, when I try to go back to a button that has already been clicked I cant load it because now the other SWF(s) are now on top. If I put an actionscript on the button that tells it to unLoad the other SWF’s or if I just assign the SWF’s to the same level the other SWF’s will just dissapear and i won’t get that effect of the image scrolling over the previous one. I need the previous SWF to stay visible while the new SWF loads on top … just like it does in the above mentioned site.

Anyone? … Thanks for your patience.