Administrator sees even non-shared items

[Radtherapy]

Using Exchange 2003 (migrating to 2007 next quarter), Outlook 2003 and 2007

We have found out that anyone with administrator permissions is able to
share a user's calendar, unless the user has specifically blocked these users.

Is there any way to automatically block administrators from having this
access? It doesn't seem productive to require users to block these people
individually.

Thanks,

BA