by Jim » Wed Dec 28, 2011 9:35 am
The only type of coupon that will affect Shipping charge is the Free shipping coupon. As far as I know there is no built in way to modify any shipping option based on the total of the cart except for adding a handling fee.
You could probably implement something like that in a custom shipping add-on. That would require writing a separate script that would return shipping options and prices based on the information passed to it. This feature is only available in Pro level ShopSite stores. Help for the feature is found at
http://www.shopsite.com/help/11.1/en-US/sc/pro/shipping.api.html
http://www.shopsite.com/help/11.1/en-US/sc/pro/shipping.api.spec.html