Sub Worksheet_Change(ByVal Target As Range)
On Error GoTo Fin: If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("C:C")) Is Nothing Then
Derlig = Sheets("suivie").Range("C65500").End(xlUp).Row
If Cells(Derlig, "C") >= 30 Then MsgBox "Veuilez planifier l'entretien préventif"
End If
Fin:
End Sub