Hmmm... I don't want to sound rude, but I'm not sure why it is needed, except for aesthetic reasons. If you want your cookies to work with all your sub-domains and directories, just set the "Cookie Domain" field to ".vbulletin.com" (change to your domain, NOTE THE TWO DOTS!), as explained in the Admin options page. Also, set the "Path to save cookies" field to "/". It is working for me, and I'm using the same cookies in different sub-domains and directories.