MS Outlook 2000/Exchange Server

I have an Exchange Calendar that needs an email account removed from it. For example, when I send an invite from this calendar, if a person replys to the invite, I and another person will get the response on behalf to that calendar. How do I remove that individual. That person no longer works for the company and their email account has been removed from the GAL, but for some reason, it won’t leave the calendar.

Help before I go bald!

Thanks a bunch