Simple paypal integration

I have web site where I need to implement a Paypal standard payments shopping cart option. Since the shopping cart will be used to reserve rooms at our small hotel, what I need is a simple way to dynamically populate one of the button options from an external source, reflecting the actual availability of rooms. Ideally, the free/busy data should be obtained from Google Calendar which I use for reservations. Other sources such as a google spreadsheet could be acceptable. If that is not possible either, then a MySQL database. The hotel is very small - only three rooms - possibly expanding to six. I am hands-on persons who understands programming, web site design, etc. The final project should be in the form of complete code (incl. paypal button html code), and a working sample page on my web (for me to further design from) with either google calender integration (preferable) or other simple (mysql-based) calender mangement function.