I have a form which has l list box of value and a set of navigation buttons defined in a class. I would like to refresh the navigation buttons when moving in the list box, assume 3 items.

1. when at line 1 down and bottom buttons are highlighed
2 when at line 2 all buttons are highlighted
3. when at line 3 up and top buttons are highlighted

This works when using the buttons. How do I do it from the list box?