A list box has an alphanumeric value. On activation, the value is the currently selected list item, or spaces if no item is selected. On output (applicable only to paged list boxes), the value is the first list item that matches the value of the substring input by the user. For example, if your list consisted of the strings "One", "Two", and "Three", an input value of "T", "Tw", or "Two" would cause "Two" to be selected. An input value of "Th" would cause "Three" to be selected. An input value that does not match any item, or a value of spaces, causes all items to be unselected.