In the Form Editor, double click on an object to display its Property List. Mac users can hold down the command key and click on any event check box in the Property List. Command + click on an empty check box will select all events. Command + click on a checked box will deselect all event check boxes.

Windows users will use the Control + click combination.

Suppose you want to assign a button object every event except the On Load event. You can select all events and deselect the On Load event instead of manually checking each event check box.