WPF Selected Item

[AirlineSim]

I have this data template in my wpf xaml to add items to my listbox.

How can I via VB.NET code access the Caty_Name when one is selected?

<DataTemplate x:Key="Caty" x:Name="CatyItem">
            <Border Background="White" BorderBrush="Black" BorderThickness="2" CornerRadius="15" Padding="10px" Margin="5px">
                <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition></RowDefinition>
                    <RowDefinition></RowDefinition>
                    <RowDefinition Height="3px"></RowDefinition>
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="30px"></ColumnDefinition>
                    <ColumnDefinition Width="200px"></ColumnDefinition>
                </Grid.ColumnDefinitions>
 
                    <TextBlock Grid.Column="1" Grid.Row="0" Margin="2" Foreground="Black" Text="{Binding Path=Name}"></TextBlock>
                <StackPanel Orientation="Horizontal" Grid.Column="1" Grid.Row="1" Margin="2">
                    <TextBlock Foreground="Black" x:Name="Caty_ID" Text="Catalogue ID:"></TextBlock>
                        <TextBlock Foreground="Black" x:Name="Caty_Name" Text="{Binding Path=CatalogueID}"></TextBlock>
                </StackPanel>
                    <Image Grid.RowSpan="2" Grid.Column="0" Grid.Row="0" Height="30px" Width="30px"  Source="catalog.gif"></Image>
                
            </Grid>
            </Border>
        </DataTemplate>