Sub Convertir()
Dim DtHr(), i&, n&, s
With Feuil1.[J1] 'Première cellule de données
n = .Parent.Cells(.Parent.Rows.Count, .Column).End(xlUp).Row
If n >= .Row Then
With .Parent.Range(.Cells, .Parent.Cells(n, .Column))
DtHr = .Value
On Error Resume Next
For i = 1 To UBound(DtHr)
If VarType(DtHr(i, 1)) = vbString Then
s = Split(DtHr(i, 1), "/")
DtHr(i, 1) = CDate(Join(Array(s(1), s(0), s(2)), "/"))
End If
Next
On Error GoTo 0
.Value = DtHr
End With
End If
End With
End Sub