|After using a lot of time on this on and there is almost none information about it on the Internet, i will then post a small blog about what i know..... so if it can help you|
In the process of trying to make a smart way to allow access to captive portal for wireless and wired connection, i made a small app there detected when the access to the Internet was limit by a captive portal page and then it got the IP numbers of this captive portal and then stored the IP number in the reg. so that the information can be used be the CSA agent for a rule.
The IP number was stored like:
HKLM\Software\MyCaptivePortalDetector\IP_001 = "22.214.171.124"
Then i made a "Network Access Control" there was using this IP number store in the reg.
the string in the "Communicating with host addresses" is "@(reg HKLM\Software\MyCaptivePortalDetector\IP_001 default=10.80.40.2)"
The default value is used when the key in the reg is not found.
The thing is that this is working, but not automatic when the key change in the reg as i hope it will have been.... it seems that CSA is only reading the key when the CSA software is starting(read: you have to reboot) and not when it just change.
so this works to limit access to only the captive portal but the user has to reboot in the process, so this is not usable to use and i have now made it in another way where i use the "add/remove process to application class".
Hope this help you on the way and not wast a lot of time also.
Captive Portal - http://en.wikipedia.org/wiki/Captive_portal