Very Simple Question, Please Help!

Okay, I am new to Flash, and for some reason or another I cannot seem to get this simple function to work. I made this button, and set the function stop(); so that the video doesn’t play. Now I want it so that when you left click the button, you will play the video. I used this code:

stop();
onMouseDown= function (){
gotoAndPlay(2)
}

But it doesn’t work. Can someone please help me out? Thank you in advance!