Yes.

  1. open the file \data\avast4.ini, and add the following to the [WebScanner] section
    UpstreamProxyHost=address_of_your_proxy_server
    UpstreamProxyPort=port_of_your_proxy_server
    (the same stuff you now have in your browser)

  2. in your browser, change the proxy settings to
    server: localhost
    port: 12080
    (this will direct all communication to the avast WebShield).

Restart the WebShield provider for the changes to become effective.

Hope this helps,
Vlk