[FMX]On button(mc) for two actions

1

How can I make a mc witch I us as a button fuctional for two actions.I mean when I press the button that a clib fades out and when I press again it fades in again I tried it with an if but the it only works one time.This is the script

 but.onRelease = function(){
 if (mc._alpha <= 1){
  fadeClip (mc, 100, 4);
 }else if (mc._alpha >= 99){
  fadeClip (mc, 0, 4);
 }
}

What is wrong ?