Sounds like a big facility,and wired with repeaters for wireless access?If so why not get converter- voip to analog{line} and assign line to pc as ext. owner also set doorphone alert to same ext,?Need ability on pc for flash type recall so you can toggle between line and intercom call.This is just a thought,I have never tried it and don't know how to access code for door release on your pc or what upgrade pc would need.Sounds like it needs to access 2 functions at same time,I asked a IT friend of mine and he mentioned dual card via usb or pc slot card so pc can be set up for dual function on network.Really only 1 call at time is possible.