rewrite rule for apache

[bituman <bituman () enerla net>]

I want to protect a directory, better to say its contents from people downloading it, 
if the are not coming from a specified page.
Now, i understand, that the following code redirect *vicodin.* to a standard error page.

RewriteEngine on
RewriteCond %{HTTP_REFERER} ^(http://)?(www\.)?.*(-|.)vicodin(-|.).*$ [NC,OR]
< ...lots of other rules go here...>
RewriteRule .* - [F,L]

What rewrite rules should i use if i want users from index.php?option=login to access the content and everyone else to 
redirected to the standard error page?
Is it even possible to use get style params in the referer field?

Thank you in advance
bituman