Change an Ical Calendar’s settings en masse?

Hi Gary,

I’ve subscribed to and imported a calendar for a football side’s fixtures for the season. I get the alarm beeps on the day, but 15 mins before. I want to change the alarm timings to beep, say, 4 hours before. Is there a way to do it at one go for all the entries or do I have to click on each one separately and change the settings?

Thanks.

— Dhruv