how to make that each worker can see only his appointmenst in google calendar?
each worker has his own google calendar.
maybe the ics file can be sent also to worker email so he can import?
each worker can share his/her google calendar with Google Account that is authorized in EA. There you can make settings to each appointment goes to calendar of particular worker. This is the section where you should do that : https://www.youtube.com/watch?v=KQ8r33WHng4