Silverlight 3 Custom Control Event-handling Navigation

Question

I have a Silverlight 3 aplication, The solution (of 3 projects) looks Like this:

ChartsCustomControl
   PieChart.cs
SLGrid.Web
SLGrid
   NavigationPage.xaml
   Views
      PieChartPage.xaml
         PieChartPage.xaml.cs

I'm using the navigation Frame control, and have a folder named Views for the different pages. PieChartPage.xaml.cs calls the pie chart custom control (ChartsCustomControl / PieChart.cs).

Inside PieChart.cs, I have successfully attached an event handler (slice_MouseLeftButtonDown) to the pie slices so that a message box comes up showing the name of the pie slice that was clicked on. But instead of the message box, I need to pass that name back to PieChartPage.xaml.cs so I can act on that pie slice click from there.

How do I do that?