I believe this concept is demonstrated in the 'Appointment Reminder' sample. If you want to display multiple appointments in an alert you could use a Timer that ticks (for example) every 5 seconds. Instead of displaying the alerts in response to the BeforeDisplayReminderDialog event, you could add the appointments for which that event is fired to a list, and then in the Timer's Tick event handler, display the alert for whatever appointment reminders came due since the last time the timer was checked.