Private Sub Worksheet_Change(ByVal Target As Range)
    ActiveSheet.Unprotect Password:="aaa"
    Dim rng As Range
    Set rng = Target.Parent.Range("B16")
    If Target.Count > 1 Then Exit Sub
    If Intersect(Target, rng) Is Nothing Then Exit Sub
    With Range("B19:E19")
        Select Case Target.Value
        Case "No"
            .Value = 0
            .Locked = True
        Case "Yes"
            .Value = ""
            .Locked = False
        End Select
    End With
    ActiveSheet.Protect Password:="aaa"
End Sub