Is it possible to create a custom "Add to Cart" button? I don't mean custom CSS or styling or anything like that (I know how to do that). I mean being able to control the function that gets called from the button.

I'd like to be able to call a function that checks to see if the customer is in one of the countries we don't ship to (already written) when they add an item to their cart.

I could probably create my own form action down there instead of using the default  <%=getCurrentAttribute('item','addToCartDrilldownHtml')%>, but I don't know how NetSuite assembles all the elements that go into that form and would be nervous that I'd leave something out.