silverlight: setting RowDetailsTemplate controls from RowDetailsVisibilityChanged

Question

Given a silverlight datagrid with RowDetailsVisibilityMode="VisibleWhenSelected", on clicking a row in the datagrid, how do you set or bind the controls in the RowDetailsVisibilityChanged() event?

        <data:DataGrid.RowDetailsTemplate>
            <DataTemplate>
                <StackPanel>
                    <TextBlock Text="a" x:Name="_txt" />
                    <ListBox x:Name="_lst"></ListBox>
                </StackPanel>
            </DataTemplate>
        </data:DataGrid.RowDetailsTemplate>