ok not quite sure if this is what you want but use ftp/file manger and edit file adminsourcesclassesbbcodecustomdefaults.php
find
//-----------------------------------------
// Adding rel='nofollow'?
//-----------------------------------------
$rels = array();
$rel = '';
$_title = '';
/* Fetch actual host for better matching */
$data = @parse_url( $option );
if ( $this->settings['posts_add_nofollow'] )
{
if ( ! stristr( $data['host'], $_SERVER['HTTP_HOST'] ) )
{
$rels[] = "nofollow";
}
}
if ( $this->settings['links_external'] )
{
if ( ! stristr( $data['host'], $_SERVER['HTTP_HOST'] ) )
{
/* Look a little closer */
$rels[] = "external";
$_title = $this->lang->words['bbc_external_link'];
}
}
if ( count($rels) )
{
$rel = " rel='" . implode( ' ', $rels ) . "'";
}
return "<a href='{$option}' class='bbc_url' title='{$_title}'{$rel}>{$content}</a>";
change the {$option} in the last lien to the http that you want it to go .