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