' <DieseOutlookSitzung>
Private WithEvents Items As Outlook.Items

Private Sub Application_Startup()
  Dim Ns As Outlook.NameSpace

  Set Ns = Application.GetNamespace("MAPI")
  Set Items = Ns.GetDefaultFolder(olFolderTasks).Items
End Sub

Private Sub Items_ItemChange(ByVal Item As Object)
  On Error Resume Next
  Dim Task As Outlook.TaskItem
  Const CategoryName As String = "(Complete)"

  If TypeOf Item Is Outlook.TaskItem Then
    Set Task = Item

    If Task.Status = olTaskComplete Then
      If LCase$(Task.Categories) <> LCase$(CategoryName) Then
        Task.Categories = CategoryName
        Task.Save
      End If
    End If
  End If
End Sub
' </DieseOutlookSitzung>