Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim X As Integer
If Not Intersect(Target, Range("plage_2")) Is Nothing Then X = 2
If Not Intersect(Target, Range("plage_3")) Is Nothing Then X = 3
On Error GoTo fin
If WorksheetFunction.CountIf(Range("plage_" & X), Target) = 3 Then
MsgBox "Nouveau triplé"
If Range("O2") = "" Then
Range("O2") = Target
Else
Range("o1").End(xlDown).Offset(1) = Target
End If
End If
fin:
End Sub