Random Number ( if's)

Hello, I wonder how I can randomly select a condition, the following code has been made, but only the condition 2 is used, as can for to be randomly selected one of theconditions?

Grateful!

var luck:Number = 3;

if (luck == 1) {

   gotoAndPlay(1);    
   return 0;
}

if(luck == 2) {

   addChild(movie);   

}


if(luck == 3) {

   gotoAndPlay(1);
   return 0;
}