Salut Helder,
j'imagine que c'est possible avec formule mais ça,... connais pas trop!
En VBA, par contre...
Double-clic sur la feuille pour démarrer la macro!
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
'
Dim tData, tSplit
'
Cancel = True
Columns(3).ClearContents
tData = Range("A1:C" & Range("A" & Rows.Count).End(xlUp).Row).Value
'
For x = 1 To UBound(tData, 1)
tSplit = Split(tData(x, 2))
For y = 0 To UBound(tSplit)
For Z = 1 To UBound(tData, 1)
If tSplit(y) = tData(Z, 1) And x <> Z Then
tData(x, 3) = tData(x, 3) & IIf(tData(x, 3) = "", tData(Z, 1), ", " & tData(Z, 1))
Exit For
End If
Next
Next
Next
Range("A1").Resize(UBound(tData, 1), 3).Value = tData
'
End Sub
A+