Thank you guys. I've learned many useful tips in the last comments.

Now I know the idea of comparing online users in RADIUS and NAS can be a good solution but since I use two different NAS types on my network, and I am almost sure both of them don't have standard API to allow other apps read their online users, It will be a little bit challenging and maybe time consuming to implement.

But whatever it is, I happy that we could come up with a solution in about 24 hours on this mailing list. :)

Thank you,

Moby