/// <summary>
/// Adiciona uma nova worksheet a uma workbook existente
/// </summary>
/// <param name="xWorkbook">workbook</param>
/// <param name="xWorksheet">nova worksheet</param>
private void updateWorkbook(XWorkbook xWorkbook, XWorksheet xWorksheet)
{
List <XWorksheet> xWorksheets = xWorkbook.getWorksheets();
xWorksheets.Add(xWorksheet);
xWorkbook.setWorksheets(xWorksheets);
}