Country list specific option/table in the Contact details page needed

Country list specific option/table in the Contact details page needed

It is important to have a country specific option/table in the    Contact details  page.

We to be sure that the organizations we work with enter always the same value ( ej.UK) and they have not the  posibility of enter other  posibilities ( ej, United kingdom, GB  , Great Britain and so on).

It is important for two reasons:

1. We need to follow the sales to other countries. I need to filter and categorize.

2. Calculation of taxes. I am based in Spain and the VAT will be different if:

a)  I am invoicing a customer based in Spain, 
b) I am invoicing a customer based in the European Union.
c) I am invoicing a  custormer based outside the  european Union.

I have to double check if this tax calculation is right and it will be easier if I have a unique  posible value for each country.

I am not asking for your help on this tax calculation, that I understand it is  difficult but only this mention option/Table  on contact details.

I don't mind if you keep the  posibility of a blank value. In this case I will use it for Spain.

Please consider using the  iso two letters country codes:

http://countrycode.org/