Private Sub worksheet_change(ByVal target As Range)
If Not Intersect(target, Range("B6:B" & Range("B65535").End(xlUp).Row + 1)) Is Nothing Then
If target = target.Offset(-1, 0) Then
Cells(target.Row, 1) = Cells(target.Row - 1, 1) + 50
Else
Cells(target.Row, 1) = 50
End If
End If
End Sub