I was tinkering around with some "workarounds" for this (a rule to automatically delegate to a user-owned resource,etc) without much luck on accomplishing this. However, it occurs to me that one technique for accomplishing this (not quite automatic)is to set the user's default alarm on new calendar entries for 4 hours, then when notify pops up four hours before the appt, user can enter "225" in the minutes field for Snooze. This won't help much if they're not present when the alarm goes off initially (because the alarm will clear w/o them changing the snooze) - unless you change the Notify parameter for how long the alarm dialog box stays open to something like several hours.