ShortTag shows you how you can create a Button with AS3:
var sb:SimpleButton = new SimpleButton();
//we create the SimpleButton object
//as you know a Button in Flash has 4 state: up, down, over and hit
//we create a MovieClip for the up, down and hit state and an other one
//for the over state
var mc:MovieClip = new MovieClip();
//we create [...]