In the Power Customer Fields example using continents and countries, you can elect a country (or several countries) in a custom field based on a continent you select in a different custom field.
The following video has information about how dependent fields work.
Script details
The options for the Continent custom field were taken from the database. The following scripts are used in this example:
string continent = argv["customfield_10109"]; //the dependent field
string[] countries = sql("myDB", "select country from countries where continent = '" + continent + "'");
return countries;