TOPIC: Lock Field Based on Selection

Hi,
I have an event i am currently running and it would be very helpful if for my event or others if you select say a time frame from 9AM-1PM that you can't Select anything in the 9AM-10AM Field or 9AM-12PM Field although the conditional fields are nice it would require them to make a selction in order to get other fields to display and some of the users may get confused by that setup. It would be nice to say if they user selects X field they can't select Y Z I think it would be fine if they displayed but if they grayed out completely so they can't book themselves for 2 events that start at 9 am . You would think people could tell time but you'd be surprised. If you could give this some thought it would be greatly appreciated. Users so far love the event registration as it looks very professional grade.
Thanks,
Tom