how to find referenced column and table

Hello everyone,

I have a db with lots of relations like this:

    create table country (
      code varchar primary key,
        name varchar not null
    );
    create table customer (
        code varchar primary key,
        name varchar not null,
        country references country (code)
    );

Now I'm building a PHP function that creates an HTML form to change one
row of table CUSTOMER. It's a generic function, it should work on any
table, and it should be able to recognise if a row references another
table, so that a pulldown list can be created dynamically. In this case
a pulldown with all COUNTRY codes in it.

    CUSTOMER
    code            [    ]
    name            [             ]
    country    [pick one...[V]

So what I'm looking for is a query that will tell me that row A of
table B references row X of table Y. How would I do this?

TIA for any pointers / help!

--
Jules Alberts.