Noob here - Mouse Down

I am trying to use a “if else” statement, and i am missing something. I want the movieclip to be transparent when the mouse is clicked on it. Here is my code i have:



box.addEventListenter(MouseEvent.MOUSE_DOWN, down);

function down(evt:MouseEvent):void {
if (evt.MOUSE_DOWN == true){
box.alpha = .5;
box.alpha = 1;

I am getting an error saying that on the function line “MOUSE_DOWN” is bad.
What am i doing wrong?