HTML in Tooltip

Question

Hi,

I am trying to add a link to a tooltip on a map but I have failed miserably. Here is my code

            Dim point As New Ellipse()
            Dim location As New Location(Data(1), Data(2))
            MapLayer.SetMapPosition(point, location)

            Dim toolTipMsg As ToolTip = New ToolTip()
            toolTipMsg.Content = Data(0) + Environment.NewLine + _
                                      "  Revenue: " + String.Format("{0:c}", Actual) + Environment.NewLine + _
                                      "  Budget: " + String.Format("{0:c}", Budget) + Environment.NewLine + _
                                      "  Variance: " + String.Format("{0:0%}", dblVariance) + _
                                      "  <a href='http://www.yahoo.com'>Test</a>"
            ToolTipService.SetToolTip(point, toolTipMsg)

            MainMapLayer.Children.Add(point)

The html link won't work. Any ideas are appreciated.

Thanks in advance