Code list integration with program

[ericdes <eric@vcardprocessor.com>]

In the case you want to limit the buyers to be either Canadian or US-based,
- you create a country code list that restricts the choice to both 
countries (OK)
- and you create 2 lists of country sub-entity codes, one for the 
Canadian provinces and one for the US states. (OK)
- and the corresponding CVA file. (OK)

(1) How do you check that the state of Texas shouldn't be used when the 
buyer is in Canada. (I guess through a Schematron rule?)

(2) And most importantly, how a program could interact with a code list 
(and with a code list only) to display a list of US states when the 
country selected is the US, and a list of Canadian states when a 
Canadian address is entered? Is this at all possible, desirable? to rely 
on a code list to govern the GUI?

Eric