Converting a sting to a movieclip

I want to convert a sting which comprises of the instance and a suffix so I can edit show my addresses.

var addressName = event.target.name + “Address”;

I tried this but is is null when I trace it.

myMap.aberdeenRed.addEventListener (MouseEvent.ROLL_OVER, showAddress);

function showAddress (event:MouseEvent) {
trace(event.target.name + “Address”);
var addressName = event.target.name + “Address”;
addressName.alpha = 0.2

}

You can use getChildByName