Hi Juan,
Regrettably, this isn't something that can be set in CaseComplete. I'm not very familiar with other server-based version control systems (TFS, Subversion, etc.), but it may be possible to set individual file permissions in systems that require users to log in. For the built-in version control - which is based on a shared folder - to work properly, however, everyone accessing the project needs to have "Full control" access level to that repository folder.
Thanks,
Jason