A response for a list box is taken whenever a selection or deselection is made. This happens when the user

•Selects an item with the mouse.

•Moves the arrow keys in a single-selection list box.

•Presses the space bar in a multiple-selection list box.

A response is taken to a multiple-selection list box whenever an entry is selected or deselected. Note that if an entry was previously selected, single- or double-clicking on the entry again will deselect that entry.