Need Some Help

I was just wondering if anyone could help me.

I have been trying to create a slideshow for a website but have found that the webpage takes too long to load so I tried to create it by using the loadMovie code.

When I tried to do it though I was having problems with masking the movie clip to create the transition I need.

I want the photo to appear for several seconds and then shrink down to nothing as the photo behind it appears.
This is what I was able to get:

But when I try to have the photo stay for a few seconds and then add the keyframe to the mask to start to shrink the whole photo disappears. Like this:

I know this is hard to describe but I was hoping that someone could help me get the effect I am looking for without having a huge load time.

Any help would be greatly appreciated.

Thanks a lot.