Help with fade in sound

Can anyone tell me how to fade in sound using AS…i just try using coding inside http://www.kennybellew.com/tutorial/ website but it still not working so can anyone help me?..

thx…

on (load){
a=0;
speed=5;
}
on (enterFrame){
if (a<100){
a=(a+speed)
YourSoundObject.setVolume(a);
}
}

ELLO CAMERAMANO…tx for ur reply anyway…i just modified ur code then i put in frame


bkgMusic = function () { 
 a=0;  	
speed=5; 
 mySound = new Sound(this); 
 mySound.attachSound("sound2");
 mySound.start(0, 3); 
 mySound.setVolume(80);
   	if(a<80){
  	   a+=speed;  		
           mySound.setVolume(a); 
 	}
  };
  bkgMusic();

it’s seem the sound not start at all…so is it something wrong with my code…any help would be greatful…thx…