Limiting timeslots for rescheduling

Hello forum!
 

I am a psychologist and will be mostly running my own scheduling by booking in appointments for my clients at the end of sessions. I'm not planning on sharing my scheduling page with clients. However, when clients need to reschedule between sessions, I want to offer them the option to do this themselves using the link in the confirmation email. 

The issue I have is that I have a couple of appointment slots (8am and 6pm) that only I wish to use. I don't wish to allow my clients be able to reschedule into these slots, but as things stand they can see that they're available on the "reschedule booking" page. Is there an option anywhere to make certain times/slots hidden for rescheduling, or to limit slots for rescheduling to certain times of the day?

Hope this makes sense!

I believe you sould be able to do this with a recurring time block out on the calendar. During this time block administrators can add appointments, but clients would not have the option to select those times.  

Thanks for the suggestion. Just tried it but I'm afraid it only sort of works. You're right that I can manually add appointments directly the calendar if there's a recurring time block, but the slot disappears entirely from the "add new>appointment" list for both me and the client.

I have a series of pre-arranged timeslots for my appointment types, and I'm looking for a way for the 8am and 6pm slots to be only visible to me, rather than having to manually add them.