Setup employee screentime monitoring

I am looking for a way to monitor the screen time of my employees. I need a very simple reporting tool which can tell me how many hours the employees were active and how many hours they were away from the screen (i should have the facility to add a timeout like say 5 mins). As multiple users work on 1 machine using RDP, I would need something that will work with concurrent users. Secondly, I need a way to offer remote assistance to them. The complication here is that I have multiple users who work on the same machine at a time, thus I can't use tools like team viewer.