Er, just so you know. The AE option I mentioned is very much the 'Super Advanced' option here. You can do it but for what you want it's a bit over-kill. Key framing the positiohn of your clip so it 'slides' off the side of the page as you pan is a one minute job (once you know how to keyframe).

You'll sit there all week getting it sorted in AE unless you already know how to do it - which I guess you don't or you wouldn't be asking would you?