Simple AJAX/Javascript Price Calculator Script

Hello, I need a simple script that will help calculate the cost of print products e.g. business cards, flyers, post cards...based on the amount & they type of features the user selects. (Best example: [login to view URL]) So the script would be able to receive the parameters and each parameter would affect the price differently, I should be able to chnage the parameters easily on the database. I want a very simplified script and I prefer AJAX code so that the changes will be reflected on the screen immediately without having to refresh/reload the page. (Another good example is : [login to view URL])