Private Sub TextBox3_BeforeUpdate(ByVal Cancel As MSForms.ReturnBoolean)
Dim i&
ComboBox1.ListIndex = -1: TextBox1 = "": TextBox2 = ""
For i = 0 To ComboBox1.ListCount - 1
If Val(TextBox3) = ComboBox1.List(i) Then
ComboBox1.ListIndex = i
Exit Sub
End If
Next i
MsgBox "Le n° " & TextBox3 & " est inconnu!", vbCritical
Cancel = True
End Sub