Accessing clips I attached?

Ok, I’m guessing there is an easy answer here but I can’t figure it out.

I’m attaching a bunch of clips like this; (mainBut is the name of the class)

for (var i = 0; i<buttons.length; i++) {

var mc = “b”+i;

mc = new mainBut;
mc.tex.text = buttons*;
mc.x = pos;
mc.y = -30;
addChild(mc);

}

So now how do I control the clips I’ve made? Say, for example, a button is supposed to tween one of the clips alpha’s to zero, how would I adress the clip. I tried b0 and it didn’t work. I hard partial success by pointing my button at ‘mc’ but that obviously only allows me to control the last button.