Sub a()
Dim dl&, formule$
dl = Sheets("Feuil2").[A65536].End(xlUp).Row
formule = _
"=IF(ISNA(VLOOKUP(RC[-1],Feuil2!R2C1:R" & dl & "C2,2,0)),"""",VLOOKUP(RC[-1],Feuil2!R2C1:R" & dl & "C2,2,0))"
With Range("B2:B" & [A65536].End(xlUp).Row)
.FormulaR1C1 = formule: .Value = .Value
End With
End Sub