ControlName = "MyControlName_L" + String.Format("{0:D2}", DoingLevel);
var MyControlButton = this.FindName(ControlName) as Button;
MyControlButton.Background = new SolidColorBrush(Colors.Orange);
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.