Unmerges the selected cells.
procedure UnmergeSelectedCells(UnmergeRows, UnmergeCols: Boolean);
If UnmergeRows=True, it unmerges each selected cell into RowSpan rows.
If UnmergeCols=True, it unmerges each selected cells into ColSpan columns.
UnmergeRows and UnmergeCells can both be True.
This method must be called when the document is formatted.
See also methods: