[MarkFL]

Okay, I got it to work:

PHP Code:

if (in_array(THIS_SCRIPT, array('showthread', 'vbcms')))
{
    if ($memberinfo['field6'])
    {
        $new_name = $memberinfo['field6'];
    }
    else
    {
        global $post;

        if (!$post)
        {
        $post = fetch_userinfo($memberinfo['userid']);
        }

        $new_name = $post['field6'];
    }

    if ($new_name)
    {
        $memberinfo['musername'] = str_replace($memberinfo['username'], $new_name, $memberinfo['musername']);
        $memberinfo['username'] = $new_name;
    }
} 


Please let me know if this takes care of what you wanted to do since you are more familiar with the system.