Dynamic InstanceName

First, I apologize if this is a repost. I’m short on time.

Basically what I want to do is target a movieClip with a dynamic instance name and move it.

I need to pass a variable “a” to target the specific instance of “new_”.

var a = 4;

for (i:Number = 0; i < 6; i++){
var menuClip = movie_mc.duplicateMovieClip(“new_”+i, i);
menuClip._x = menuClip.width * i;
bnt.onPress = function(a){
[a]._y = 300; //— THIS DOESN"T DO IT OF COURSE