very simple motion question

[Algreco]

Sorry to even post this.

I want to move a movie clip from x = 0 to x = 500, then to x = 20 and finally to x = 600.
how do i do it?
my script at the moment (is wring) is:

//clip stands already on x = 0//

if (this._x >=500){//sending it to x = 500
targetx = 0;// it bounces back to x = 0
}
if (this._x <= 20)){//but on the way it meets x = 20
targetx = 600;//so it runs towards x = 600
}

Sorry for this silly question
I think I need to use either variables by setting the limitations as true and false or do something with "do while", or "switch" with cases or something, but i'm a little stuck here....
I actually would be happy if the boundries could be defined with a variable cause I would like to call on a masking effect once the movie clip reaches the appropriate point.
help?

[Mattias Robo]

[script]
switch (this._x) {
   case 0:
      targetx = 500;
      break;
   case 20:
      targetx = 600;
      break;
   case 500:
      targetx = 20;
      break;
   case 600:
      targetx = 0;
}
[/script]

[Algreco]

thnx Mattias, that's what i was after.
regards,
Al