Within Teamwork.com, you can set privacy on any milestones you add to your project so only certain users can access them.
You can set privacy on milestones when first creating them on your project or when editing an existing milestone.
In the new milestone modal, go to the Privacy & Followers tab and select the current setting under Who can see it. By default, privacy will be set to Everybody on the project.
In the privacy modal, you can switch between people and teams. Privacy can be set to individual project members, entire companies, or teams.
You can use the search field at the top to locate specific people. Click the filters button on the right for additional options on who should be selectable in the People and Teams tabs.
To change the privacy of an existing milestone, hover over the milestone in the project's Milestones tab and select Edit.
Note: Site administrators in the owner company will always be selected (gray) in the privacy settings as their permissions override privacy by default. They will always be able to see the item.
For more information, see: Adding a Milestone