You can start writing a script with the following command on the server, executed when the user login the session, replace 3389 with your port number
netstat -aon | findstr ESTAB | findstr 3389 >>\\ShareFolder\connections.txt
https://www.howtonetworking.com/RemoteAccess/ts19.htm
Check if the file is being created and if it contains external client addresses. Next, you can write a script on MikroTik parsing this file on a schedule or a script for Windows working with MikroTik via API - this way looks preferable.