Here's what I came up with:
sorry for the poor quality, it's a gif after all
This was made using the same Track Matte on three clips in Premiere.
I first made this matte in photoshop.
It's a simple rectangle path, I converted to a 'selection' with a feathered edge of 20. Then filled with white paint.
It was saved with a transperant background. I imported it into Premiere. Set it's transperancy to Alpha Channel. Then keyframed the Transform effect under Perspective to animate the matte going acorss the screen.

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From there, I exported as a uncompressed avi. Then imported it into a project where I had three images(though you could use clips as well). I setup the images transperancy to "Track Matte". Then placed the animated matte on the track above each clip. Each clip with it's matte is offset about 1second from the perevious clip. If they were all together they would overlap.
Once rendered you get the finished project that was seen above.
~klinky