Forums Scripts & Popups ban user from using text command

How to ban user from using ONTEXT command that is available for all users? I need that it saves banned users on .hsh ot .txt file.
So if i type !ban nick2 it will ban nick2 from using ontext command, and if the ontext command is !add and banned user uses it, it shows - You are banning from using this command, and if user is not banned it do what it should do. Hope you understand.