Continuous horizontal movement with AS?

Kirupa has a tutorial on continuous movement of clouds (motion tweening).
Does anybody know about a AS code for this kind of movement?
I know we can move the MC from A to B, but for continuous movement what is the condition if we get to a final point?

if (this._x <= 100) {
this._x += speed;
What is the code here if this._x IS 100? How get back to the start point? without gap in the movie?

mx-guest2004 :slight_smile: