Merci, cela fonctionne parfaitement: voila ma solution :
Sub ClassDir()
Dim s As String, i As Integer, p As Integer, LastRow As Long
LastRow = Sheets("Importation_Données" ).Range("B" & Rows.Count).End(xlUp).Row
i = 3
p = 3
Range("A3" ).Select
For p = 3 To LastRow
If (("B" & i) <> "" ) Then
'MsgBox "" + "B" & i
s = Application.WorksheetFunction.VLookup(Sheets("Importation_Données" ).Range("B" & i), Sheets("Tables" ).Range("A3:B27" ), 2, False)
Selection.Value = s
i = i + 1
Range("A" & i).Select
End If
Next p
MsgBox ("Traitement terminé" )
End Sub