Change pathauto generated URL of node
I found what I needed. It is the function hook_url_outbound_alter...

function myModule_crawler_url_outbound_alter(&amp;$path, &amp;$options = FALSE, $original_path){
    $mother_nid = $options['entity']-&gt;field_mother_series_nid["und"][0]["value"];
        if( $mother_nid &gt; 0 ){
            $path = "CLEAN-URL/".$mother_nid;
            $options['alias'] = "CLEAN-URL/".$mother_nid;
        }
}


Thanks for helping!!!