Shipping applied per category

Looking for an extension that will enable a shipping amount per category to be applied. So for example if I have categories called Box, Ball and Triangle, I want to apply a single shipping amount to all products in the Box category of products and different rates to the other two categories.

Does one already exist?
Does anyone have a similar extension they are willing to sell?
Is anyone willing to develop such an extension and if so at what price?

Thanks

I use this and it's very good

http://www.opencart.com/index.php?route ... on_id=2684