Private Sub Worksheet_Change(ByVal Target As Range)
Application.ScreenUpdating = 0
Rows("13:21").EntireRow.Hidden = False
If Range("b11").Value = "A" Then Range("16:21").EntireRow.Hidden = True
If Range("b11").Value = "B" Then Range("13:15,19:21").EntireRow.Hidden = True
If Range("b11").Value = "C" Then Range("13:18").EntireRow.Hidden = True
Application.ScreenUpdating = -1
End Sub