Here's the javascript I'm using. I've tried it both with standard DOM javascript and JQuery, both do the same thing. The number on the page updates but when you click add to cart the number isn't there. Manually updating the number changes it just fine,
(for some reason the textarea won't let me paaste the code)
I get a var with javascript.document.GetElement and do a (var).value = 5 (or "5" or '5')
or I get a JQuery selector and do a (selector).val(5) (or "5" or '5')
The value on screen updates but when I click on add to cart, the pre-javascript/jquery value is what gets sent to the shopping cart.