Actually don't worry, I discovered I needed to add this at the beginning:
Actionscript Code:
var u:String = 'SCastleExit';
And then change the code to:
Actionscript Code:
} else if (lvlArray[i] == 'SCastleExit'){
            //mcCastleExit
            var newPlacementu:mcCastleExit = new mcCastleExit();
            CastleExitHolder.addChild(newPlacementu);
        }
Just thought I'd post that for others