You can see docs an download Skeleton plugin at this link
http://docs.easy-profile.com/index.php/article/triggers
We have changed the link some months ago due to update our doc site
With skeleton plugin you can also make a operations between fields, for example:
triggerProfileUpdate($user,&$data,$changed,$isNew){
$data['sum_field'] = $data['operator1_field'] + $data['operator2_field'];
}