as2 to as3 questions

NOTE: I know I could make a class for this, but I was hoping to know how to do this without making a class just for the line mc.

Want to do something very simple, I have a mc thats a line, I am able to place it just fine… heres the deal in as2 I could do

line.onEnterFrame = function() {
this._y +4
}

however, I have this in as3…and it moves the full stage, how would I go about doing this so that It only moves the line mc (note: a new line mc is made every 2 seconds)


addEventListener(Event.ENTER_FRAME,bg);
function bg(event:Event) {
timer ++;
if (timer == 30) {
	timer=0;
var myImageMovie:line = new line();
myImageMovie.y = 20;
myImageMovie.addEventListener(Event.ENTER_FRAME,linecode)

bgmc.addChild (myImageMovie);


}

}
function linecode(event:Event) {
	this.y +=3
}