Shared Outlook Calendar - help!

Hi.

I have a shared outlook calendar in outlook 2010.  I'd like to allow a small group of people read/write access, then a larger group to have read only access, and couldn't figure out how to set that up.  I was able to grant the read/write access to the smaller group, but then the larger group couldn't see the details of the meetings ect.

Is there a way to do this?

Thank you.