How can I set different Tooltip text for each item in a listbox?

private ITypeOfObjectsBoundToListBox DetermineHoveredItem()
    {
        Point screenPosition = ListBox.MousePosition;
        Point listBoxClientAreaPosition = listBox.PointToClient(screenPosition);

        int hoveredIndex = listBox.IndexFromPoint(listBoxClientAreaPosition);
        if (hoveredIndex != -1)
            return listBox.Items[hoveredIndex] as ITypeOfObjectsBoundToListBox;
        else
            return null;
    }

public static class MouseInput
{
    // TME_HOVER
    // The caller wants hover notification. Notification is delivered as a
    // WM_MOUSEHOVER message.  If the caller requests hover tracking while
    // hover tracking is already active, the hover timer will be reset.

    private const int TME_HOVER = 0x1;

    private struct TRACKMOUSEEVENT
    {
        // Size of the structure - calculated in the constructor
        public int cbSize;

        // value that we'll set to specify we want to start over Mouse Hover and get
        // notification when the hover has happened
        public int dwFlags;

        // Handle to what's interested in the event
        public IntPtr hwndTrack;

        // How long it takes for a hover to occur
        public int dwHoverTime;

        // Setting things up specifically for a simple reset
        public TRACKMOUSEEVENT(IntPtr hWnd)
        {
            this.cbSize = Marshal.SizeOf(typeof(TRACKMOUSEEVENT));
            this.hwndTrack = hWnd;
            this.dwHoverTime = SystemInformation.MouseHoverTime;
            this.dwFlags = TME_HOVER;
        }

    }

    // Declaration of the Win32API function
    [DllImport("user32")]
    private static extern bool TrackMouseEvent(ref TRACKMOUSEEVENT lpEventTrack);

    public static void ResetMouseHover(IntPtr windowTrackingMouseHandle)
    {
        // Set up the parameter collection for the API call so that the appropriate
        // control fires the event
        TRACKMOUSEEVENT parameterBag = new TRACKMOUSEEVENT(windowTrackingMouseHandle);

        // The actual API call
        TrackMouseEvent(ref parameterBag);
    }

<ListBox Width="400" Margin="10" ItemsSource="{Binding Source={StaticResource myTodoList}}">
<ListBox.ItemTemplate>
     <DataTemplate>
           <TextBlock Text="{Binding Path=TaskName}" ToolTipService.ToolTip="{Binding Path=TaskName}"/>
     </DataTemplate>
   </ListBox.ItemTemplate>
 </ListBox>

int hoveredIndex = -1;

    private void lstCars_MouseMove(object sender, MouseEventArgs e)
    {
        int newHoveredIndex = lstCars.IndexFromPoint(e.Location);

        if (hoveredIndex != newHoveredIndex)
        {
            hoveredIndex = newHoveredIndex;
            if (hoveredIndex > -1)
            {
                tt1.Active = false;
                tt1.SetToolTip(lstCars, ((Car)lstCars.Items[hoveredIndex]).InsuranceGroup);
                tt1.Active = true;
            }
        }
    }

<Style x:Key="radioListBox" TargetType="ListBox" BasedOn="{StaticResource {x:Type ListBox}}">
    <Setter Property="BorderThickness" Value="0" />
    <Setter Property="Margin" Value="5" />
    <Setter Property="Background" Value="{x:Null}" />
    <Setter Property="ItemContainerStyle">
        <Setter.Value>
            <Style TargetType="ListBoxItem" BasedOn="{StaticResource {x:Type ListBoxItem}}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="ListBoxItem">
                            <Grid Background="Transparent">
                                <RadioButton Focusable="False" IsHitTestVisible="False" IsChecked="{TemplateBinding IsSelected}" Content="{Binding MyName}"/>
                            </Grid>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
                <Setter Property="ToolTip" Value="{Binding MyToolTip}" />
            </Style>
        </Setter.Value>
    </Setter>
</Style>