Configuring per pound shipping

[Guest]

Here is what I am wanting to do.

 

First, I will ship to 3 different zones. The US, Canada and Internationally.

 

Second, each has a rate of $x.xx for the first pound of weight and then an additional $ .xx per pound after that. The base price and additional cost per zone will vary so I know that I nned to install the zone shipping module.

 

However here is where I am stuck.

 

In order to keep from having to configure, say the US zone rates to read : 1:5.45,2:6.20,2:6.95, etc, I want to instead configure the shipping to reflect the per additional pound price.

 

Hope that makes sense and that someone has an idea or can direct me to a thread or contribution for this.