File changes when someone connects and checks out a CAL?

Gents - 

I'm trying to setup a file based trigger for healthy monitoring for a 2012 terminal license server. Should be easy right? It would be if I can sort out what file or registry key changes when someone successfully connects?

I tried to see if when a user connects and checks out a device cal if any of the files change in the C:\Windows\System32\lserver\ folder, but they don't upon successful client connection. 

Does anyone know what file or reg key on the server has a time stamp update or changes when a device successfully connects and checks out a cal?

Thank you.