you could do it in VB2 easily, just by saying something like this:
Code:
<?PHP
require 'global.php';
if ($bbuserinfo[userid] == 0) { include 'ssi-login.php'; }
else { include 'ssi-stats.php'; }
and the stats would contain a query that draws up their info, or using the $bbuserinfo tag you can draw up [posts] or [username].
But with VB3, im not so sure how to do it. Best bet is to take a look at the coding in VB3 and check out how they look for unknown users.