Animation when mouse button is held down?

I am trying to make a scope view and I need the guy to move closer to the camera for this. I want to play the animation when the right mouse button is held down. This animation isn't working but when I press "right click" the print "scope view" is printed even thought the animation is not played. Help? (Yes all the names of the scripts/animations are correctly spelled).

function Start () {

}

function Update () {

if (Input.GetMouseButtonDown(1)) ;

animation.Play ("scope") ;

print ("scope view") ;

crossfade = true ;

}