CB's suggestion would work if you add an HTTP profile to the outbound HTTP virtual server. For HTTPS, you would need a cert--which all clients accept as valid for any external domain--in order to decrypt, inspect and modify the HTTP. I would be very curious to hear whether you have such a certificate and key...
And I'm not sure I like the idea of helping a country's major backbone provider block access to external sites for the country. There are numerous ways to bypass such attempts as seen with the great firewall of China and the Iranian attempts at censorship.
Aaron