Rewrite Based On Query String

Hi, and thanks for any help in advance.

I'm looking to set up redirection to a subdirectory, but not if there is a certain parameter passed in, resource

What i want is for a url that doesn't contain either ?resource or &resource to redirect to one single file, say index.php and for all others to redirect to the same location but in the resources dir, for example http://example.com/site/styles/screen.css?resource to redirect to http://example.com/site/resources/style ... s?resource

Any help would be greatly appreciated...