/// <summary>
 /// Print the current workbook to the printer else to the default printer.
 /// </summary>
 /// <param name="printerToUse">the printer name to print the document to.</param>
 protected void PrintWorkbook(string printerToUse = "")
 {
     _workbook.PrintOut(
         _refMissing,
         _refMissing,
         _refMissing,
         _refMissing,
         _refMissing,
         _refMissing,
         _refMissing,
         _refMissing);
 }