proxy only certain assets based on host header?

[amagad]

We're trying to proxy only certain assets like png|jpg|css only when the
host header is a certain DNS name. I tried to do this in the proxy.conf file
using something the example below but it doesnt like the if statement. Is
there a way to have nginx do what I am looking for?


if ($http_host = dnsname.com) {
  location ~ ^/(stylesheets|images|javascripts|tools|flash|components)/ {
    proxy_pass http://assethost
  }
}

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,239494,239494#msg-239494