Sub Concatener()
If [A2] = "" Then [C1] = [A1] Else [C1] = Join(Application.Transpose([A1].CurrentRegion), ", ")
End Sub
Sub ConcatenerSansDoublon()
Dim tablo, d As Object, i&
tablo = [A1].CurrentRegion.Resize(, 2) 'matrice, plus rapide, au moins 2 éléments
Set d = CreateObject("Scripting.Dictionary")
d.CompareMode = vbTextCompare 'la casse est ignorée
For i = 1 To UBound(tablo): d(tablo(i, 1)) = "": Next 'liste sans doublon
[C1] = Join(d.keys, ", ")
End Sub