Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column <> 4 Then Exit Sub
If InStr(1, Target, "mois", vbTextCompare) = 0 And Target <> "" Then
Target = DateDiff("yyyy", Target, Now()) & " ans, " & _
DateDiff("m", Target, Now()) Mod 12 & " mois"
End If
End Sub