How to sync a public calendar with another public or private calendar?

I'm sure this has been asked and successfully answered before, but EE is designed that normal users like myself don't get to see answered and so are forced to ask again and again. So here we go:

Is there any builtin way to do this, or am I looking at buyng Add2Exchange? If I am, any opinions on it or its competition?

I have Exchange 2003 and mostly Outlook 2003. I want a public calendar that should be the Master, and any change to it should propagate to other calendars automatically, be they public or private.

It seems a simple and often requested feature. Did MS really leave this out? Do other email servers do this out of the box?

Thanks all.