How to split a movie file into 3 equal parts then render individual files

Hello all!

I have a client that has given me a folder full of video files that are 2160 x 540. I am trying to create a small utility that I can load these movies into that will split said movie into 3 equal parts then re-render them as 3 separate files of 720 x 540. Any ideas on the best method for this? I have been playing with scissors a bit but havent quite got it a slick as I wanted... Any help would be great. Thank you