I have developed a website to promote seminars. I would like to be able to plug-in a function where the user could sign-up for a seminar and pay online using Paypal or some other means and be able to track the number of people who have sign-up and paid. Once the seminar capacity is reached then that seminar will display something like "sold out" and not allow more sign-ups for that event. It must be easy to add more events and to easy input the capacity (count) for each event. Nothing fancy, but want to be able to easily installl within my website.