Hey Galac – that’s a really interesting question!
I’m going to assume that what you need here is multiple private calendars per client (ie, they can’t see one another’s exercise programs) and, if so, I’m afraid that isn’t supported without further customization work.
If privacy isn’t a concern, or even if it is and you are interested in discovering more about how you might do this, then please do grab a copy of The Events Calendar (it’s free!) and take it for a spin.
If you need further support, an Events Calendar PRO license is well worth the investment as besides adding a raft of great features to our core calendar offering it will allow you to access our premium forums and our awesome support team.
(Please note though that even if you purchase a license the degree of support we can provided for any advanced customization work is typically very limited, though we always work hard to point folks in the right direction even if we can’t help further ourselves.)
I hope that helps 🙂