Calendar report filtered by loginuser

Hello,
I have a calendar view that I've set up a criteria to only let the loginuser view entry's they've made. See below:

(Service_Status != "Completed" && Added_User == zoho.loginuser)

This works great!... Now the twist.

Say I need to transfer a created service request to another technician. Naturally if I change the assigned technician to another technician it only appears in the form. Using the above criteria the newly assigned technician never sees the service request on their filtered calendar. I tried to change the <Added_User> field and creator displayed "cannot change system fields".

I have an employee form that holds all of a technicians information but I can not figure out how to pull out a tech ID and use that as a filter in the calendar report.

Any thoughts would be greatly appreciated.
Alan