proxy_no_cache issue

[msony]

I understand you can use proxy_no_cache to update the cache, my setup is
like this:
          proxy_cache_valid  200 302  20m;
            proxy_cache_valid  404      1m;
            proxy_no_cache $http_my_secret_header;

And I send the header like this : curl -H "My-Secret-Header: 1" 
"www.example.com"

Which seems to pull the updated information, however if I understand it
properly it should update the cache with latest response. But it's not
doing that, all the new hits are pulling information from cache till
actually cache expires. Any idea on how to do this properly ?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,104020,104020#msg-104020