FSSO DC mode - FSSO_Guest_Users

Greetings to you

Currently FSSO DC Mode is running and working prefect !  FSSO Agent installed in Active directory and connected with FG.

Problem :

users who is not in domain appears as FSSO_Guest_Users ( like mobile )

The Plan :

I Would like if users not in domain and connect to our network one he try to access internet it should appear a Captive Portal page login and request to put his user name and password that stored in Active directory to access Internet that is !

Question : how we can do that ?

Thank you for your time