Private Sub Workbook_Open()
Const mdp = 1
Dim J As Date, der&, i&
J = Date - 1
With Sheets("Feuil1")
.Unprotect mdp
.Cells.Locked = False
der = .Cells(.Rows.Count, "a").End(xlUp).Row
If der >= 9 Then
For i = 9 To der
If .Cells(i, "a") <= J Then
.Cells(i, "b").Resize(, 3).Locked = True
End If
Next i
End If
.Protect mdp
End With
End Sub