Option Explicit
Sub TheTwiceTracker()
Dim TheRange As Range, Cell As Range
Dim TheString As String
Dim i As Integer
With Sheets('TaFeuille')
Set TheRange = .Range('A1:A' & .Range('A1000').End(xlUp).Row)
For Each Cell In TheRange
TheString = Cell & Cell.Offset(0, 1)
For i = 1 To TheRange.Rows.Count
If Not Cell.Offset(0, 2) = 'OK' Then
If TheString = .Range('A' & i) & .Range('B' & i) Then
If Not i = Cell.Row Then
.Range('C' & i) = 'OK'
End If
End If
End If
Next i
Next Cell
End With
End Sub