Mointor and control remote connections

Hi

We have several different servers running specialised software from different companies.
These providers use either Teamviewer or RealVNC to connect to our servers and network.
But I am not comfortable with the fact that they can access the servers whenever they like, uncontrolled and unmonitored.
Is there a way that I can issue them an access ticket of sorts that will only open Teamviewer/VNC access from set IP for a certain time period?
And record why the person accessed the network?
Any ideas?

Using a RB 750 with OS 5.12. Fixed IP ADSL line connects to 750.

Thanks in advance