def add_worksheet(name = nil)
      if name.nil? then
        n = 0

        begin
          name = SHEET_NAME_TEMPLATE % (n += 1)
        end until self[name].nil?
      end

      new_worksheet = Worksheet.new(:workbook => self, :sheet_name => name)
      worksheets << new_worksheet
      new_worksheet
    end
def add_worksheet(name = nil)
      if name.nil? then
        n = 0

        begin
          name = SHEET_NAME_TEMPLATE % (n += 1)
        end until self[name].nil?
      end

      new_worksheet = Worksheet.new(:workbook => self, :sheet_name => name)
      worksheets << new_worksheet
      new_worksheet
    end
Create new simple worksheet and add it to the workbook worksheets

 @param [String] The name for the new worksheet