show posts based on country (custom_fields)

I installed 2 plugins:

http://wordpress.org/extend/plugins/just-custom-fields/
http://wordpress.org/extend/plugins/ip2country/

ip2country displays the country code correctly using:

<?php
$ip2country = ip2country();
echo $ip2country->country_code;
?>

and just custom field displays all the countries I have ticked by checkboxes by using:

<?php
$countries = get_post_meta($post->ID, 'post_geo', true);
?>

and

<?php
foreach($countries as $country) echo $country.',';
?>

I’ve read the_loop references, but i’m afraid i’ll end up messing it up.. can anyone help me with the code I should be putting in my loop to only show posts based on if the ip2country_code isin custom_field_array