Defines mode of cell selection. The modes available are:
Flow- Allows the range of cells to be selected between the start index and the end index, which also includes the other cells of the selected rows in the pivot table.
Box- Allows you to select a range of cells within the starting and ending column indexes that are included in the range between row cells in the pivot table.
BoxWithBorder- Allows the range of cells to be selected as the box mode, but along with the borders in the pivot table.