Using Time Slots in SharePoint 2007 calendar

Is there a way to create a SharePoint 2007 calendar that only allows users to input appointments in certain time slots? I would like the time slots to run Monday thru Friday from 8am - 10am, 10am - 12pm, 1pm - 3pm, 3pm - 5pm, and 5pm - 7pm. Only one person can sign up in a time slot at a time.

I do not want to have to enter every date from no开发者_开发百科w till the end of time, which is the how this solution works: http://sharepointsolutions.blogspot.com/2009/02/give-blood-to-your-workflow.html

That is a great solution for the one-time Blood Drive type of time slotting but not exactly what I need.

I would either :

• adapt the new form or create a custom one that will prevent people from adding a new event outside of your specified time slots and ensure that a specific time slot is not registered by someone else prior to save it. That will allow you to create a dedicated UI with relevant controls (eg : dropdown lists that have only the hours that you specified)

• add an event handler on ItemUpdating that will ensure that there is no collision with another event and validate your business requirement regarding time slot. You can then transfer to an error page with a proper explanation message

Both solutions require custom development. I would be glad to hear if there is something out of the box that would fulfill this need.