Change default country for addresses at runtime

Hi ,

I am about to set up a zencart where we can ship products to multiple countries . The url is http://www.mithaimate.com . We have a drop down where the user is first asked to select the delivery country and is then shown products according to that .

What I want is to change the default country for shipping and billing address at runtime depending on some user action . Is there a way I can change the zencart default country from user to user at runtime depending on some input etc. ?

another way to put this problem would be ..
i could set some session variable depending on some user action ...and the country drop down has a particular country preselected depending on that session variable value...