Private Sub TextBox1_Change()
Dim D As Date, S As Long
On Error Resume Next
D = CDate(TextBox1.Text)
If Err Then LabInfoDate.Caption = "Date non valide": Exit Sub
On Erreur GoTo 0
S = (Day(D) - 1) \ 7 + 1
LabInfoDate.Caption = S & IIf(S = 1, "er ", "ème ") & Format(D, "dddd ""de"" mmmm yyyy")
End Sub