Converting 16/9 HD Widescreen to 4/3 HD Fullscreen

[dellsam34]

Hi everyone;
I have a footage that is 1920x1080 m2ts that I want to crop horizontally to 1440x1080 square pixel 4/3 aspect ratio by loosing the left and right side portions of the widescreen frame which is fine for the purpose that I'm doing it for, However I need someone to show me how to use key frames on Vegas because the 4/3 frame is not going to be always in the center, It changes as the scenes go by, it could be at the far left or at the far right or anywhere in between, I need to do that precisely using key frames at scene changes, In other words, If one person is on the left side of the 16/9 frame I want the cropped 4/3 frame on the far left and so forth, just like they do it on full screen movies.

So anyone familiar with Vegas that can give me some steps on how to get this done? Thanks

[dellsam34]

Anyone familiar with Sony Vegas?