A Border object represents a border around a cell or area of cells.
You can also define part of a cell's border using Border.Item(Border.Part):
|Sets or returns the color of the border, as an ExcelWriter
Color object. If multiple colors were assigned to border parts,
Color will return the color of the top border.
|Sets or returns the border's line style.
|Returns a BorderPart object representing the specified part of the border. This is the indexer for the Border object.