Sub doublons()
Dim der&, dic, t, i&, j&, s, clef, ligne
Application.ScreenUpdating = False
If Me.FilterMode Then Me.ShowAllData
Columns("f").Font.ColorIndex = xlColorIndexAutomatic
der = Cells(Rows.Count, "f").End(xlUp).Row
Set dic = CreateObject("scripting.dictionary")
t = Range("f1:f" & der)
For i = 2 To UBound(t)
t(i, 1) = Replace(t(i, 1), Chr(10), " ")
t(i, 1) = Application.Trim(t(i, 1))
s = Split(t(i, 1))
For j = 0 To UBound(s)
If Not dic.exists(s(j)) Then dic.Add s(j), ""
dic(s(j)) = Trim(dic(s(j)) & " " & i)
Next j
Next i
For Each clef In dic
s = Split(dic(clef))
If UBound(s) > 0 Then
For Each ligne In s
i = InStr(Cells(Val(ligne), "f"), clef)
Cells(Val(ligne), "f").Characters(Start:=i, Length:=Len(clef)).Font.Color = vbRed
Next ligne
End If
Next clef
End Sub