Sharing sub calendars

Hi,

I have 2 users with an issue. User 1 has a main calendar, and 4 sub calendars. I have setup the permissions on all 5 calendars from outlook so User2 has reviewer permission.

When adding the calendar to User2's outlook, no matter what I try I can only view User1's main calendar not the sub calendars.

How do I make the others visible?

Thanks,

A.