Child movieclips in for loops

programming flash
1

I want to attach 4 child clips to one master clip and then control them in a for loop but I can’t get the mc variable to work right.
It traces the right name but AS doesn’t seem to like it and won’t change the _x

for(i=0;i<4;i++){
master.attachMovie(“noob”, “noob”+i,i, {_y:100});
}

for (j=0;j<4;j++){[COLOR=Red]
mc=[‘master.noob’+j];
mc._x = 100+(5*j);[/COLOR]
}