Attendees on Custom Event Entity

[shanebat]

I have seen 1 post on this topic about 12 months ago but did not see any clear answer.
Is it possible to add attendee to a custom Calendar Event?
I have tried from entity manager etc, is it only possible in code or via the Entity and Manager?
I understand it wont be compatible with Google Calendar Sync but that is not a problem in my instance.

Thanks for any help
Shane