VIEWING PRIVATE APPTS IN OUTLOOK/EXC

We run Exchange Server 5.5 and Outlook’97 on the desktop.
A Manager is sharing his Calendar out to his PA and we have set her permissions on his calendar to be maximum at “Owner” level.
Apparently a feature of this is that if the Manager marks anyappointments in his Outlook calendar as “Private” then on her screen she should still see the time blocked off on his calendar and the text “Private Appointment” against it.
This however isn’t happening!! Anyone any ideas on this one?