Sharepoint Calendar: Block a Day Off

Does anyone know of a way to prevent access to, or highlight, a specific day in a Sharepoint calendar? The intent is to show which day(s) are not available for a given task.

I have already fashioned a Workflow that would email a user, but it needs to be visual as well - people need to see at a glance what days are avaiable.

Any have any ideas? I'm running on SBS 2008 with WSS 3.0 .. I also have Sharepoint Des开发者_JS百科igner 2007 installed, if it can be leveraged.

Personally, I would do this by creating a new event receiver to run on the calendar. This event receiver should run on new / updates, and should configure item level permissions for any event on that specific day. If you break the item's permission inheritance, and remove read access to all items on that day, no one would be able to see the task.

Obviously, always be very careful when working with item level permissions.