Outlook 2007 Global Calendar

We are currently using Exchange 2003 along with Outlook 2007 and want to know if there is a way to make a “global” calendar. Basically we want to show everyone’s in/out status on a single calendar that everyone can access and update. I know that you can have calendars on Sharepoint but we want to try and do it only in Outlook. I also know about Group Schedules, but that’s not what we want. Is there a way to create a common calendar that everyone in the office can access? Thanks!