wordpress in subdirectory vbulletin in root

I have vbulletin in the root and i want to use wordpress with permalinks in a /blog folder.

i have spent two days reading and trying every combination of rewrite rules if statements and all sorts of odd lookign hacks.

Basically i have rewrite rules for dbseo (vbulletin plugin) in my root server block for SEO friendly urls.

I need to understand how i create the wordpress pretty permalinks in the /blog/ location block with it ignoring anything in the root for requests that include /blog/ in the url.

Thanks in advance.