Workbook_SheetSelectionChange

Impossible faire passer le code ci dessous : j'ai des cellule avec fond couleur et souhaite les verrouiller par le code suivant :
Private Sub Workbook_Open()
If ThisWorkbook.BuiltinDocumentProperties("Author").Value = "haha" Then
Application.DisplayFullScreen = False
Application.DisplayFormulaBar = True
ActiveSheet.Unprotect Password:="haha"
Else
Application.DisplayFullScreen = False
Application.DisplayFormulaBar = False
End If
End Sub

Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
With ActiveCell
.Locked = True <----------- c'est là que ca plante
.FormulaHidden = True
End With
If ThisWorkbook.BuiltinDocumentProperties("Author").Value <> "haha" Then
ElseIf Target.Interior.Color = RGB(255, 192, 0) Then
ActiveCell.Locked = False
ActiveCell.FormulaHidden = False
End If
End Sub