Sourcing Data from Custom Record Into Item

Hello All,

We are doing some standard costing calculations in NS and what I wanted to do was create a custom record type that would store all the country information as well as the freight weight information.  The idea is that for each record in the custom record type it would be the name of the country and then the rate stored.

What I want to do is then create a field in the item record that allows us to chooose from the list of countries in the custom record type. 

Here is when things get tricky.  I need to then be able to interpret what rate is connected to that country that was just chosen and then add that into a formula field that takes other values into consideration at the item level and produces a value.  Also, what needs to happen is that if I were to go change the rate in the custom record for that country, all the item calculations will be updated based on that rate as well.