Within Teamwork Projects you can create a calendar event and associate it with a specific project on your site.
To create a new event, go to the Calendar area:
When creating an event in the calendar you can choose the privacy tab to select a specific project to associate the event with from the drop-down:
When selecting a project this means that only people with permissions for that project will see the event in the calendar view.
You can tell if the privacy on an event has been associated with all or specific projects if the 'person' icon below is showing next to the meeting time:
For more information see: Creating recurring events