Option Explicit: Option Base 1
Sub Doublons()
Dim DL, i, N, Tablo
Application.ScreenUpdating = False: N = 1
DL = Range("A1000000").End(xlUp).Row
ReDim Tablo(DL)
[B:B].ClearContents
For i = 2 To DL
If Application.CountIf(Range("A2:A" & i), Cells(i, "A")) > 1 Then Tablo(i) = "Doublon"
N = N + 1
If N = 100 Then
Application.StatusBar = "Progression : " & i
N = 0
End If
Next i
Range("B1").Resize(UBound(Tablo), 1).Value = Application.Transpose(Tablo)
Application.StatusBar = ""
End Sub