How to customize the Tooltip of the Cube Dimension Browser

public MainPage()

        {

            InitializeComponent();

            this.DataContext = new ViewModel.ViewModel();

            this.olapClient.Loaded += (send, e) =>

            {

                this.olapClient.CubeDimensionBrowser.MouseMove += new System.Windows.Input.MouseEventHandler(CubeDimensionBrowser_MouseMove);

            };

        }

        void CubeDimensionBrowser_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)

        {

            if (this.olapClient.CubeDimensionBrowser.ItemsSource is MetaTreeNodeCollection)

            {

                object obj = null;

                 if (e.OriginalSource is TextBlock)

                {

                    var a = (e.OriginalSource as TextBlock);

                    //ToolTipService.SetToolTip(a, a.Text);

                    var itemSource = (this.olapClient.CubeDimensionBrowser.ItemsSource as MetaTreeNodeCollection)[0];

                    foreach (var item in itemSource.ChildNodes)

                    {

                        if (item.Caption == a.Text)

                        {

                            obj = item;

                            break;

                        }

                    }

                    if (obj != null)

                    {

                        TextBlock tb = new TextBlock();

                        tb.Text = (obj as MetaTreeNode).NodeType + " : " + (obj as MetaTreeNode).Caption;

                        ToolTipService.SetToolTip(a, tb);

                    }

                    else

                    {

                        if(a.Text == "Growth in Customer Base")

                            ToolTipService.SetToolTip(a, "Shows the KPI for Growth in Customer Base");

                    }

                }

            }

        }