I am writting a db to monitor my machine capacity. Suppose I have 3 machines A, B and C, I create a form to the user to register/book the machine before they use. Let's say I register machine A on 12.12.2002, 15:00-17:00, another user might register with machine A too on 12.12.2002, 16:00-18:00. How to make the db prompt for time/schedule conflict in this case? Please advise. Thank you.