writing an app to limit/firewall a pc to one url

[weekender]

ok so i need to have a dissertation title in four weeks time. what i'm thinking of, is a 'web customisation interface' - a website where users can login and they get a location bar within the page. This would then cause the php server to read in the page, apply a function to the html and output it to the browser.

For example, the php could strip rude words, and so act as a parental filter. Or it could use the high-speed backbone of the php server to pull in the larger images on the page and downsize them, allowing the user to see them faster. Or it could be used to change contrast on sites that may be hard to read for certain people.

So the server works as a passthru, taking in a page and relaying it in a form more suited to the audience.

For this to work as a secure app (for the parental filter, for example) I would need to limit the computer to that particular url, so that no pages could be loaded outside of the relay.

I need to know thoughts on how best to do this. I would much rather do it in delphi or vb, but am learning java at the moment. I see this being a small app which runs maybe in the system tray, and can only be disabled with an admin password, so functioning as a basic firewall. I know I can use these languages to close http ports, thus blocking all urls, but need to let the one through.

Sorry it's a bit longwinded - any help or advice would be MUCH appreciated.

thanks,

adam