OT: anyone use a Yahoo calendar?

I use my Yahoo calendar quite a bit, I depend on it and it works great.
But I'm a member of some yahoo groups and if a spammer comes along and
fills up the group calendar with spam it also shows up in my personal
calendar. No problem if the admin will delete it but sometimes it takes
days or weeks before they get around to it, most don't even know they have
a calendar. Does anyone know how to stop group items from showing on my
calendar? I've searched yahoo but there is nothing about it.