Private Sub Worksheet_Change(ByVal Target As Range)
Dim Mois$, An&
If Target.Address <> "$G$5" Then Exit Sub
Application.EnableEvents = False
Mois = Format(Target, "mmm"): An = Year(Target)
Range("c7") = "Stock " & Mois & " " & An - 2
Range("c8") = "Stock " & Mois & " " & An - 1
Range("c9") = "Stock " & Mois & " " & An
Application.EnableEvents = True
End Sub