Gerardo,
Looks like a few people in two different threads are trying to help with this, without making you happy.

Maybe we don't exactly understand what you are trying to do. Can you explain, in a perfect world, how this would work, so we can try to help approximate that?
My understanding is that you want your staff to make a an entry when some one no-shows. You want to be able to run a report, say at the end of the month, giving a list of those patients. Then you want to write a letter to each patient (or call them) asking them to reschedule. Is that correct or is there more to it?