Anyone familiar with GOP?

I would like to manually edit 1 or more gops to be able to cut my movie.
I can only cut at keyframes, so I need to rearrange the gop structure, I need to put a keyframe where I want to cut the movie, and fill the space before and after with I's and P's.
Correct me if I'm wrong but i think you can only split the avi into 2 at keyframes?!!