Set an alert for an event in a subscribed calendar in iCal My meetup.com account allows me to subscribe to an iCal calendar that displays all meetups that I have RSVP'd "yes" to.

All of the events appear as expected, but none of them have an alert setting (e.g., display message 2 hours before).

Is there a way to set an alert for events in a read-only subscribed calendar?
My workaround, annoying as it is, is to copy the subscribed event to my main calendar and set my alerts from the copy.