Shared Resource Problem

I am using Exchange 5.5 and Outlook 98. The problem I am having is that I have a bunch of conference rooms (like 5) and would like to have certain people directly book meetings. Each conference room is setup as its own mailbox. With Outlook I have found that it will not automatically accept meeting requests unless the mailbox is open. So now my question is how have multiple mailboxes open at the same on one machine so it will accept the requests. And yes, I know how to have one profile open multiple box at the same time but it does not automatically accept the meetings. Is there a setting here that I am just not seeing? Or if there is a better way to set this up – please let me know.