watch selected rows

Sub ShowOnlyCertainRows()
Dim RowNum As Long, LR As Long, Rw As Long

RowNum = Application.InputBox("Show rows that are multiple of what number?", "Multiples of...", 3, Type:=1)
If RowNum = 0 Then Exit Sub

Application.ScreenUpdating = False
With ActiveSheet
    .UsedRange.Rows.Hidden = False       'unhides all rows, doesn't work on AutoFilter

    LR = .Range("A" & .Rows.Count).End(xlUp).Row

    For Rw = 1 To LR
        If .Range("A" & Rw).Row Mod RowNum <> 0 Then .Rows(Rw).Hidden = True
    Next Rw
End With
Application.ScreenUpdating = True

End Sub