Playing a different audio clip after another has finished

Hello, I have a script that should play an audio clip after the default one is finished. I havent gotten any errors from unity and i got the script from the unity script reference. But when i try it in my game it doesnt play the second clip. Here is my script.

var otherClip: AudioClip;
function Update () 
{
audio.Play();

yield WaitForSeconds (audio.clip.length);

audio.clip = otherClip;
audio.Play();

}

Thanks for any help!

var otherClip: AudioClip;
var playNow = false;

yield WaitForSeconds (audio.clip.length);
playNow = true;

function Update () 
{

 if(playNow)
 {
  // Assign the other clip and play it
  audio.clip = otherClip; 
  audio.Play(); 
  playNow = false;
 }

}