Sound class

Hi.
I’m brand new to Flash.

In the attached file I am trying to adapt something I got from a tutorial book.
The sound’s behaviour is controlled ok - plays, then locks play until it’s finished.
How can I change the code so that only the button starts the audio clip instead of the onMouseDown function?

NB: I know that I could attach the sound to the button timeline but I don’t want to do this.

Thanks,
Adamb