def label(name)
      labels = workbook.defined_names
      return [nil, nil, nil] if labels.empty? || !labels.key?(name)

      [labels[name].row, labels[name].col, labels[name].sheet]
    end
def label(name)
      labels = workbook.defined_names
      return [nil, nil, nil] if labels.empty? || !labels.key?(name)

      [labels[name].row, labels[name].col, labels[name].sheet]
    end
returns the row,col values of the labelled cell
 (nil,nil) if label is not defined