I'll try 2/3 I'm sure I've done these with no success.... 1 won't work, as people will know if it shows busy, there on leave (it's all were using this for at the moment)

@ Ray,

i was using this and causing an error

[('id', 'child_of', [employee.id for employee in user.employee_ids])]

so manager or anyone above could see.... dont suppose you want to point out where i went wrong?

The way to think about a domain for a record rule is "COLUMN ON THE RECORD I WANT TO CONTROL ACCESS TO" "OPERATOR" "VALUE". So you are asking Odoo to restrict access to events where "ID" - but ID is a value assigned by the database and will be different for each database - instead of ID you should have a field on the event that represents something you can compare with VALUE? What field on the Event do you think is a good candidate to compare with a value or some kind (the second part of your domain).