Wipe Effect

I’m trying to create a split-screen or wipe effect between two sets of levels in the same view so we can wipe from “before” to “after”. Ideally, UE would have level transition effect track with more options than just the “fade” effect we have now. In the meantime how can we have different levels (or different sets of objects) visible to different cameras? And, how can we overlay camera views so that we can animate a mask to wipe from one to another?
Thanks very much in advance!
-Donald Newlands