Removing attendees from meetings

Hi

I use Outlook 2003 to schedule programmes/workshops for 20 or more calenders
and often hold dates in multiple calendars. For example I may send out a
meeting request to 5 people to hold dates for a workshop. Once the
resourcing is decided I may only need 3 out of the 5 people. How do I
uninvite or remove the unnecessary people from the meeting request and stop
any updated meeting requests being sent to them in the future. Often there
is confusion when colleagues who know they aren't needed for
programmes/workshops still get updated meeting requests and time is wasted by
having to explain that it is the way that Outlook works which seems to
prevent removing them from the meeting altogether.

I am hoping someone can shed some light on how to get around this issue

Thanks