Option Explicit
Private Sub Workbook_Open()
Dim AnnJQuAu As Date
On Error Resume Next
AnnJQuAu = [AnnuléJusquAu]
If Err Then
AnnJQuAu = DateSerial(Year(Date), Month(Date), 1)
Me.Names.Add "AnnuléJusquAu", AnnJQuAu: End If
On Error GoTo 0
If Date < AnnJQuAu Then Exit Sub
If MsgBox("Message de début " & Format(AnnJQuAu, "mmmm yyyy") & "." _
& vbLf & "Annulez pour ne plus l'afficher.", _
vbInformation + vbOKCancel, Me.Name) = vbOK Then Exit Sub
AnnJQuAu = DateSerial(Year(AnnJQuAu), Month(AnnJQuAu) + 1, 1)
Me.Names.Add "AnnuléJusquAu", AnnJQuAu
End Sub