Help With GUI Stop and play other Sound ?

Hi guys, i have created this script it basically plays a song when clicked on and that's all good but i would like to ask your help with something. what i want to do is if i click on my GUI button while the song is playing i want it to stop the track. This is if i click on the same GUI if the music is playing.

Here is the script :

var MyAudioTrack1Naruto : AudioClip; //var MyAudioTrack2Naruto : AudioClip; //var MyAudioTrack3Naruto : AudioClip; //var MyAudioTrack4Naruto : AudioClip; //var MyAudioTrack5Naruto : AudioClip;

  function OnGUI () { 

    //Make the first button

     if(GUI.Button (Rect(10, 20,105,20),  "Play Track 1 (Naruto Enter) ")){
        if (!audio.isPlaying){
             audio.Stop(); //if something else is playing stop it and then play track 
              audio.clip = MyAudioTrack1Naruto;
                  audio.PlayOneShot(MyAudioTrack1Naruto);    

                        }
                            }
                                }

Oh and thanks in advance :)