procedure PriorRow(ShiftKey, CtrlKey: Boolean=False)

 The ShiftKey and CtrlKey parameters control how multiple row selection occurs in relation to the row navigation. When the ShiftKey parameter is True, then the range of selected rows is extended to include all rows between the current row index and the row at the new index. When the CtrlKey parameter is True, then the set of selected rows is extended to include the new row at the new index.