Continuous Scrolling..again


I need to have a movie clip loop in the background but need to have it so that it is smooth and seemlessly endless. Anyone know how to do this? I need to do it with script rather than motion tween because i want to be able to control the speed of it. Anyone got any ideas?

Thanks nathan99 for your help so far. The loop is good except that i cant get it to seem smooth. Once the loop has finished it jumps back to the start of the loop. Anyother ideas?