Viewing ALL User calendars thru Exchange

Is it possible to view all user calenders on ONE calendar so I can get a good idea of what everyone’s doing.

I know there are third party applications that can do this however I basically want to filter out everyones vacation days so I know who’s in and who’s out.

It doesn’t necessarily have to be in a calendar view, a report would be just fine. I know Crystal Reports can do it however I’m only able to extract my local calendar and can’t query a global calendar.

Any suggestions?