[1project2many]

The original locks were actually a combination of two locks. Locking the outside handle consisted of turning the lock cylinder in the pushbutton so the button could not be pressed. The door could be opened from the inside but could not be opened from the outside.

Locking from the inside meant lifting the handle and engaging a lock mechanism in the latch. The outside button could press the latch linkage but the latch would not release. The door could only be opened from the inside by releasing the lock to press the handle down.

If you are trying to prevent the outside button from being pressed, maybe it's an easy matter to use a solenoid to slide a blocking device between exterior button and the lock linkage? If you are trying to lock the inside latch you might want an electric lock motor to pull on the door handle rod to lock the door.