payment form options like this site

Hi how would a form option like this be created? there is one button used for various prices and im guessing it posts form data and it uses paypal ipn.


I have looked at all the code and cannot find what is controlling the system. Everything to do with the form is in general.js

many thanks

Jquery UI is what they used, I think.

EDIT - tried to post link to it, no go.

This is the library they use for that form: jquery-ui-1.8.16.custom.min.js
They use general.js to control how the contact form behaves