One possible option in this case would be to get a reference to the item(s) in the legend, and set a mouse over handler:
telerikChart.DefaultView.ChartLegend.Items.MouseEnter += new MouseEventHandler(MainPage_MouseEnter);
void MainPage_MouseEnter(object sender, MouseEventArgs e)
MessageBox.Show("Mouse over element");
I hope this gets you started properly.
the Telerik team
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