Combine 4 movies into one (showing synchronously in the new movie)

Hi,

I have got 4 avi movie files with same time length. But I want to combine them together and make a new movie showing 4 movies at the same time in one display, which means the frames are combined together, not the time length.

Are there any build-in subroutines to help doing that, or maybe some easy methods?

Many thanks, Lawrence