Shared calendar, delete own entries only

[4610silbro]

Hi everyone
I have a few resources and calendars that are shared. What I did to share them is use the zmmailbox command and share it for the whole domain with the rights: ri
Is there a way to set the permission so that only the creater or owner of his entry can modify and delete it? For example:
room1 - shared resource for the whole domain

user1 - creates and entry

user2 - cant edit or delete user1's entry

user1 - can edit or delete his entry
Is this possible?
I use the newest Zimbra (8.0.7) and Ubuntu 12.04 LTS
Thank you very much in advance :)

Silvio