ecart charges for a click box

I have a cart with 10 static items, i have extra services that come with each product. What i want to do is have 3 selection boxes that when they are selected they add extra charges to the cart?

see the following tutorial for details on adding product options:
http://www.webassist.com/tutorials/Add-static-product-options-eCommerce-Series

to modify this so that the option changes the price, you would need to add a calculation.

using the tutorials example of a Color option, and charging 1 dollar more if a color is selected, the calculation would be:
Name: TruePrice
abs([Color] != '')?[Price] + 1:[Price]

then edit the totalPrice Calculation:
(abs([Color] != '')?[Price] + 1:[Price]) * [Quantity]

In the cart display, remove the Price binding, and replace it with the truePrice binding, and in the code that passes the order to the Gateway, change it to pass the truePrice binding in place of the price binding.

Jason i have a few issues i can get the list onto the add to cart page & when i select yes or no it appears in my cart as yes or no, but when i try to insert your calculation firstly the cart wont let me do it in the initial window, i have to hit ok & then go into bindings. When i go in there i can add it in. Every time i add in this calculation & preview the file on my local server its blank & when i delete the calculation & preview the file it re-appears?

I reviewed the example but i want mine to be a tickbox & not a dropdown menu?

The Calculation should be added to the eCart object.

Go to Insert -> WebAssist -> eCart -> eCart object to open the eCart object floater.

in the eCart Object floater, select your eCart object and click the edit button. create the calculation on the calculations tab.

NOTE: the calculation above is an example, the example uses a column named Color. If your column uses a different name, you will need to adjust the example code.

If you want to use a checkbox, you will need to edit the code that is produced by the add to cart button behavior. in the add to cart button behavior, set the column to be updatable from a textbox, then in code view, change the type attribute:
type="text"

to be a checkbox
type="checkbox"