Hey there @Carlo05236 - great question + thanks for posting!

There are a couple of options, here. 

Firstly, create a one-on-one event type that will hold your availability for most invitees (clients), then Share Your Calendly Link for that event type via whatever method you prefer.

For the clients that you’d prefer to provide custom availability: 

• consider our One-Off Meeting type (click to learn more)
• consider our Customize Once and Share feature (click to learn more)
• if this is an ongoing need and you’d prefer not to create a one-off meeting and/or customize once and share an existing event type each time, simply create a secondary one-on-one event type with Monday-only availability, make that ET “secret” and only share it with those clients you’d like to book on Mondays only

This short Loom video goes over how to make an ET secret: 

I hope this helps!

Thank you very much!!! 
great answer. :-)

I’ll better explain my need: I’d like to create a GROUP calendar with 10 seats available for each time slot, then my needs are:

1. Give availability for student X to book only on Mondays and student Y only on Tuesdays
2.  in the slot 12.30-13.30 there will be only 3 seats available instead of 10.

Obviously, seats available for everyone in the main group calendar should be less than 10 if student X books on Monday. 
I mean that seats available in group cal should updates based also on student X,Y bookings. 
 

looking forward for your response. Have a great day! 

Hey again @Carlo05236 -- thanks for the clarification!

At this time there is no way to make it so one invitee can book on days X and another on days Y within the same event type, as all availability for that Group Event Type will apply to everyone booking. The best bet here is still going to be to create two separate group ETs with different availability and send them to the appropriate invitees (students). There is also no way to set up automated changes like you’re asking for. 

However, once you’ve created a group ET you can actually go in and make it so that different time slots have different invitee limits (3 vs 10).

Read about that below: 

I hope this helps!