Shot in the dark (LDAP related)

Slim chances of getting an answer, but this might save hours of googling...
I have a users group (domain local) and some of the users are part of a trusted domain.
When listing the members I can see the user listed under "member"
[member] => Array (
[count] => 1
[0] =>( CN=S-1-5-21-0123456789-012345678-0123456678-0123,CN=ForeignSecurityPrincipals,DC=MY_DOMAIN_NAM E))

Now how do I link this with the actual user of the trusted domain???
I can connect to the DC of the trusted domain and maybe do a search on users - but the GUID of the users looks like '3a6b43fa2fec5a4e94ecfd5e2210bad1'. How do I cross-reference the 2 values???
This whole thing is needed for integrated NT authentication on my webserver for users of the trusted domain...

Found a solution here: http://us.php.net/ldap_get_values_len