I've this code:

<IfModule mod_rewrite.c> 
RewriteEngine On
RewriteCond %{ENV:REDIRECT_SUBDOMAIN} ="" 
RewriteCond %{HTTP_HOST} ^(www\.)?([a-z0-9][-a-z0-9]+)\.mysite\.com\.?(:80)?$ [NC] 
RewriteCond %{DOCUMENT_ROOT}/userdata/%2 -d 
RewriteRule ^(.*) index.php/frontend/index/%2/$1 [E=SUBDOMAIN:%2,L] 
RewriteRule ^ - [E=SUBDOMAIN:%{ENV:REDIRECT_SUBDOMAIN},L] 
</ifModule>

ErrorDocument 404 /ext/404.php

which virtually redirects user.mysite.com to mysite.com/index.php/frontend/index/user (it's looking at codeigniter, this isn't the issue)

it really works perfectly however I wish to add the feature when a person types in user.mysite.com/blog, it is going to mysite.com/index.php/frontend/blog/user. used to do it such as this:

<IfModule mod_rewrite.c> 
RewriteEngine On

RewriteCond %{ENV:REDIRECT_SUBDOMAIN} ="" 
RewriteCond %{HTTP_HOST} ^(www\.)?([a-z0-9][-a-z0-9]+)\.fourthdraft\.com(/[a-z0-9][-a-z0-9]+)?$ [NC] 
RewriteCond %{DOCUMENT_ROOT}/userdata/%2 -d 

RewriteCond %3 ^/blog$
RewriteRule ^(.*) index.php/frontend/blog/%2 [E=SUBDOMAIN:%2,L] 

RewriteCond %3 !^blog$
RewriteRule ^(.*) index.php/frontend/index/%2/$1 [E=SUBDOMAIN:%2,L] 
RewriteRule ^ - [E=SUBDOMAIN:%{ENV:REDIRECT_SUBDOMAIN},L] 
</ifModule>

ErrorDocument 404 /ext/404.php

the thing is what I am attempting to do here right? When the 'blog' section isn't given, just visit the general rule. it feels as though i am coding it wrong but you get the drift. I am beginning to understand apache