Shared Calendar with WebDav Server Problem

[Jim G]

I have a client who needs to share his calendars with his secretary. I setup
webdav on his apache server using these directions

http://fedoranews.org/mediawiki/index.php/Building_a_Simple_Calendar_Server_with_Fedora_and_WebDAV

I was able to publish his calendar to the server, have his secretary
download and view the calendar, but she got a permission denied when she
tried to edit it. I looked on the Microsoft site and found this page

http://office.microsoft.com/en-us/outlook/HA012302491033.aspx

But it tells me to click change sharing permissions and I am not seeing this
option. Is this only for Ms Exchange users? He does not have exchange and
would prefer not to use the microsoft online calendar service. This is
Office 2007.

Any ideas?

Thanks
Jim