Yes, lookup functions are what you need. Here is an example from the UPS module:
<?php
$shipper_zone = uc_get_zone_code($store['zone']);
$shipper_country = uc_get_country_data(array('country_id' => $store['country']));
$shipper_country = $shipper_country[0]['country_iso_code_2'];
?>
Joined: 08/07/2007