How to add sub-Wifi with no internet access?

[cheaterastic]

I have a router that has a Wi-Fi Multi-SSID feature with up to 4 SSID.
I wanted to enable the 2nd one with no internet access, only for network use only like localhost website, and etc.

Any way to have a sub-Wifi with no internet access?

 

[cheaterastic]

Anyone can help me? I can't find a way. I made a own website and for just my own service only for my Customers and I wanted them to connect to my Wi-Fi without an internet access. So that the only purpose for them is to visit my localhost and to choose some item.