working with 2 database help please

[miz]

ok i have 2 dbs on same host
1 is vbulletin and the 2nd is just some info
i need about things

now mysql user have axx to both databases

so i thought ok vbulletin will use $DB_site and for the other info ill user
$predb

so when im doing $Db_site->query($query)
its will run on vbulletin db
and when im doing $predb->query($query) its will run on the other database

sounds simple right ?

so i edited config.php and added $predbname = '';
so i can use it for $predb

also i open init.php to add new db_class
and added this code :

PHP Code:

 $predb = new DB_Sql_vb;
    $predb->appname = 'Pre';
    $predb->appshortname = 'pre (' . VB_AREA . ')';
    $predb->database = $predbname;

    $predb->connect($servername, $dbusername, $dbpassword, $usepconnect); 


now my problem is like that
every time server tries to connect to host he connect to db in $predb
so he wont find vbulletin info

now my qustion is if there any way that i can use this method
with out doing mysql_select_db every time i want to use $predb instead of $DB_site ???

help appricated. thanx
MiZ