Create overwrite protection module for appointment book

Easy work for experienced coder. I have an appoinment book which already protects against overwrites for "Recurring" appointments. However, I do not have an overwrite protection for users who would be entering appointments for day to day. For example: If a user would book an appointment at 10 am with Reba for 1 hour, and then the user mistakenly tries to book at 9 am for 2 hours, the 1 hour appointment is overwritten.( it's actually still in the database, but not viewable on the screen). I want to make sure that a user will receive a warning message that they are about to overwrite the appointment that they are making. This should be in a function or module that can be called from withing the program. ## Deliverables 1) Complete and fully-functional working program(s) and complete source code of all work done. 2) Exclusive and complete copyrights to all work purchased. (No GPL, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site). ## Platform Program is written in vb6 and uses mdac.