For loop to control buttons

1

i tried to use for to control all the buttons i have
but i get this error:
1083: Syntax error: dot is unexpected.
do not know what is missing

var btnNum:Number = 6;
for (var i:Number = 1; i <= btnNum; i++) {
        ["L" + i + "_mc"].buttonMode = true;
        ["L" + i + "_mc"].addEventListener(MouseEvent.MOUSE_OVER, onOver, false, 0, true);
        ["L" + i + "_mc"].addEventListener(MouseEvent.MOUSE_OUT, onOut, false, 0, true);
}
 
function onOver(e:MouseEvent):void {
        e.target.gotoAndPlay("over");
}
 
function onOut(e:MouseEvent):void {
        e.target.gotoAndPlay("out");