Mod_rewrite expression to NOT match a whole word

[elija]

This is probably really easy, but it is driving me nuts.

I have a .htaccess as shown below that works. It will send anything with /admin to the secure port. And then it will correctly rewrite the urls.

What I need to do is send anything on HTTPS that is NOT for /admin to the HTTP port.

RewriteEngine on
Options +FollowSymLinks

RewriteBase /

RewriteCond %{SERVER_PORT} ^80$
RewriteRule ^admin/?$ https://%{HTTP_HOST}/admin [L]

RewriteCond %{SERVER_PORT} ^443$
RewriteRule ^(?!admin)/?$ http://%{HTTP_POST}/$1 [L]
###  HERE I want to send any HTTPS request NOT to /admin/ to HTTP the above doesn't work..

RewriteRule ^([^/\.]+)/?$ /index.php?page=$1 [L]

How do I say not "admin" - I seem to be able to do not a or not d and so on!
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