starts looking from the given cell.
- The evaluation of PreviousCell will not result in the selection or insertion point's changing position.
- If the requested cell is not available, PreviousCell will return None.
- In the list returned by PreviousCell[cellobj,All], the first element will be the cell directly above the currently evaluating cell, the second element will be the cell previous to that one, and so on.
- PreviousCell supports all the same options as Cells.
Introduced in 2014