Please see the link attached. http://www.blackberryforums.com/afte...calendar+share
or search for Calendar Share.
I have been using this app for 2 months now and its heaven sent!
I have my calendar on there which I set up to share with my gf so she can add things on her calendar and I can see it on mine (done via Google)
The link above provide all details necessary, it does takes a little time to understand and setup but once you get it going, its all gravy from there!
Have fun. Message me if need help