set-selection

Selects or deselects a choice item. For selection, if a different choice is currently selected in a single-selection list box, it is automatically deselected.

• (send a-wx:list-box set-selection n select?) -> void
      n : small integer
      select? = #t : boolean

  If select? is #f, the nth item is deselected; otherwise it is selected. List box choices are numbered from 0.