modifying functions.php

[meowmeow]

I want to modify the fetch_userinfo() function such that: it retrieves userid, username & password from another database. (this only for the normal users)
otherwise, (admins & moderators) retrieve the data from the VB3 database!)

I have done this to check what can be done

PHP Code:

    if($userid != $DB_site->myQuery("SELECT userid FROM user WHERE userid = ".$userid))
 {
do nothing
}
ELSE 
{
    do normal function.  
} 


This gives me an error "call to undefined function myquery()"
where do I go to define a query??