Help: cache or not by cookie

[nfn]

Hello,

Sorry for bumping this topic but I was trying to setup a similar configuration.
I want to show cached pages for a refresh of 6 min to guests (cookie user=guest) and to members (cookie user=usergroup)

Am I able to read the value from the cookie? How?
How do I add X-Accel-Expires: 0 to nginx?

Thanks

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,3173,3898#msg-3898