Array onEnterFrame Problem

programming flash
1

why does this not work

printGroup.printBtn.onRelease = function () {

var oNames:Array = new Array();
    oNames[0] = webGroup;
    oNames[1] = brandingGroup;
printGroup.onEnterFrame = function () {    
    oNames._alpha -= 3;
        if (oNames._alpha <= 40){
            oNames._alpha = 40;    
        }
}

}

but this does

printGroup.printBtn.onRelease = function () {

    oNames = brandingGroup;
printGroup.onEnterFrame = function () {    
    oNames._alpha -= 3;
        if (oNames._alpha <= 40){
            oNames._alpha = 40;    
        }
}

}

as soon as i put an object into an array it stops working with onEnterFrame