Ultra Cart Help (API)

Hi, I have a product html page with 3 products, user is able to select a one product from them. I'm using radio buttons to do the selection. I want to intergrate this with Ultracart, all you need to do is make the radio butttons fuctional, means when user select products from radio buttons update the ultara cart, that's all. I want the help with that and I'm expecting the budget less than $30. Thanks