dont play animation if it is already playing

is there a way to stop an animation from playing if it is already playing?

something like if (animation.isPlaying("run"){ !animation.Play("run"); }

^^ btw that doesnt seem to work

if (!animation.IsPlaying("run") && Input.GetKeyDown ("w"))
{
}
else{
        animation.Play("mouseOverEffect");
}

Maybe that's what you mean? You need to capitalize the i in Is.

http://unity3d.com/support/documentation/ScriptReference/Animation.IsPlaying.html

You want to stop animation if it's already playing? Then try this:

if (animation.IsPlaying("run"))
{
   animation.Stop("run");
}