Code:
public static string CreateRandomWord(int WordLength)
        {
            double _rndNumHolder;
            
            string allowedChars = "ABCDEFGHJKLMNOPQRSTUVWXYZ0123456789";
            string NewWord = "";
            for (int i = 0; i < WordLength;i++ )
            {
                lock (rNum) // Lock down the call to create a random number
                {
                    _rndNumHolder = rNum.NextDouble();
                }
                NewWord += allowedChars[(int)((allowedChars.Length) * _rndNumHolder)];
            }
            return NewWord;
        }