You can define a special external access right for each data record, this can be used to restrict the general external access right. This maximum external access right to a data record applies:
A special external access right to a data record applies to all users who have direct external access to you, or have inherited external access to you via other users.
You activate one of the following options private or confidential in a data record window.
All levels for external access rights are defined in the Select participants window using the Maximum external access drop-down list.
Together with a colleague you create an appointment. You colleague should see the keyword and tags fields, but not be able to move the appointment. Other users should be able to access the content of the appointment.
Open the Rights assignment drop-down list and select Read.
Now, only you and your colleague can see the appointment and also those users who are permitted to see confidential appointments from either your or your colleague.
If nobody else should see the appointment except for you and your colleague, then you should select private as the Maximum external access right.