Getting listbox item value


Need some advice here.

I want to use a list box which will contain names of movies.

When one of the names in the listbox is clicked I would like it to change a movie in my container.

I got the whole container load/unload thing working using buttons, but I would like to use a srollable listbox as I have about 150 movies that will be in the list.

I just cant seem to figure out a way of getting the value of the item selected in the listbox and coverting this action into a command to change the movie in my container.

All answers greatly appreciated.