Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Select Case Target.Column
Case 2
If Target.Offset(, -1) <> "Oui" Then MsgBox "nan nan!!": Target.Offset(, -1).Select: Exit Sub
Case 1
If Target.Value <> "Oui" Then Target.Offset(, 1) = ""
End Select
End Sub