I used it once on a site for catering (I think - foreign language) where someone could only make reservations on days where there wasn't already something planned.
Basically, the way it works is by using the Blog mode. Using the Blog template, you check to see if the output says "There is no event...". If that shows up, you display the form for someone to do a reservation. If there is an event, then the event is shown and you give a message saying "Sorry, this date is reserved".
Not really hard, but you have to know how to use output buffering (ob_start and ob_get_clean).
As the previous implementation was for a paying client, I cannot provide this solution for free. You can contact me using the link below to work out the details.
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