Redmine

Hello,
We are testing Redmine to see if we can adapt it to our way of working. We are testing all possibilities and one thing that we would need is to restrict the access to the time entries custom properties by Roles, is this possible?
We only saw the workflow by is an Issue level, is this possible at time entrie level? The idea is that only a project manager could change some custom properties in the time entries, would it be possible? Some other idea to get something like this? Is there any plugin that could help us to get this?
Thank you very much for your great job.