Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
Application.EnableEvents = False
If Len(Target) = 8 And IsNumeric(Target) Then
Target = Format(Left(Target, 2) & ":" & Mid(Target, 3, 2), "hh\hmm") & Chr(10) & Format(Mid(Target, 5, 2) & ":" & Right(Target, 2), "hh\hmm")
Else
MsgBox "Saisie erronée"
End If
Application.EnableEvents = True
End Sub