Juan,
I posted some code close to what you might want here: http://moodle.org/mod/forum/discuss.php?d=125867. If you are running Moodle 1.9.9x with source since January of this year, be aware that updates to Moodle will require updates to a few of the mdl_mnet_host* and mdl_mnet_service* tables to get xml-rpc calls working.
HTH,
Bill