There is one area where you MAY be able to configure this, but I'm not sure. Definitely worth a try!
Open NIS. Click on Options (at the top, next to Help) -> Internet Security. Click on the Web Content tab. Click on Add Site (bottom left corner). Enter the site(s) you want to allow & uncheck the appropriate box(es) under the Global & User Settings tabs - so they don't conflict with each other as far as possible. You'll have to carefully experiment with the settings to get it to work to your needs/satisfaction. Post back to let us know how you got on, & if successful how you did it. Good luck, G