Option Explicit
Sub Essai()
Dim s$: s = ActiveCell: If s = "" Then Exit Sub
Dim T, D1 As Date, D2 As Date, A%, M As Byte, J As Byte, i%
T = Split(s, Chr$(10))
For i = 0 To UBound(T)
s = Left$(T(i), 8)
A = 2000 + Right$(s, 2): M = Mid$(s, 4, 2): J = Left$(s, 2)
D2 = DateSerial(A, M, J): If D2 > D1 Then D1 = D2
Next i
MsgBox "La date la plus récente est :" _
& vbLf & vbLf & "le " & Format(D1, "dd-mm-yy")
End Sub