How to disable previously selected dates in Google Calendar?

Without 2-way sync with Google Calendar still useless. I do not want people to book a slot when it is not available.

Greetings and thank you for your message.

To resolve this problem, you are able to use an Appointment field. This field will disable previously selected dates and it is possible to integrate it with the Google Calendar.

To learn more please click here.

Let us know if this solution will work for you.