Is there a way to have the Automatic Replies (Out of Office message) turn on and off automatically based on business hours? It would be great if an email came in after 5pm and it automatically receives an 'out of office' response. (this would need to be a server-side rule to function correctly)

Upgrade to Exchange 2007 or higher and Outlook 2007. The functionality is built in. No other way that I am aware of natively. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

I know the schedule is set for the start and stop time for the OoO autoreply. I'm looking for an automated setting that enables daily at certain time and turns off at a set time.

Without third party software, the only option available to you is to configure the OOTO message settings in Outlook. OOTO is not a setting managed by the server. OOTO can be managed through Web Services on Exchange 2010, as it can be set through OWA, but that is the latest version involved. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources