Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("C4:C50,G4:G20")) Is Nothing Then Exit Sub
Dim Plage As Range, L%
Set Plage = Range("G4:G20"): [A1] = ""
For L = 4 To 50
If Cells(L, 3) <> "" And Application.CountIf(Plage, Cells(L, 3)) > 0 Then [A1] = Cells(L, 3)
Next L
End Sub