I have a lot of experience in web applications development. I have developed many websites using PHP, MySQL, jQuery, Javascript, AJAX, HTML5, Wordpress, Facebook API, etc. I can develop your pop up code to be shown to user if he leaves your site without using any of your links.
You can check my reviews to get an idea of quality of my work. Please discuss further so that I can start working on your project. Looking forward to hear from you. Thanks :)