I suggest that you have just one table for calendar bookings.
Included among the fields will be the userid of the person you are booking with. That can come off a relationship to a table of users so you have control over who is bookable.
There can be a report for My Calendar entries where the filter where the [Appointment with userid] is the current user.
You can also have an <ask the user> report so that the person who wants ot book with "Fred" would answer the question with "Fred" form the drop down and then see only Fred's calendar and hence they could see where his time slots are free.
