This property is available at run time only. Columns or rows that do not exist can not be active. This property returns null if there are no active cells.
fpSpread1.ActiveSheet.SetActiveCell(2, 2);
label1.Text = "The active cell is located at " + fpSpread1.ActiveSheet.ActiveCell.ToString();
FpSpread1.ActiveSheet.SetActiveCell(2, 2)
Label1.Text = "The active cell is located at " & FpSpread1.ActiveSheet.ActiveCell.ToString()