You can remove their Permission.
Try having a look at what permissions you have given them:
Show the Folder List View in the Navigation Pane.
Right click your calendar | properties | permissions.
What is the Defalt set to? I hope it's "none". If not, change it to None.
This means your whole organisation has No permission to your Calendar.
Do those people's names show with a permissions beside them? If so, you can
remove their permission here.
Judy Gleeson
MVP Outlook
Trainer and Consultant
read my articles here:
www.judygleeson.com
Canberra, Australia
how to post questions:
http://support.microsoft.com/?id=555375