In order to make something similar to your request, you should create, as Castillo said, a table holding every player as a row. Inside each row, you should place a variable depending on whether it's disabled (true) or not. By default, everything is false in a table. So, you create a commandHandler setting their table[player] equal to false.
That's done, one step more. You must add a if-check inside the function where you outputChatBox in order to send (or not) the message. Please, don't watch out the spoiler unless you tried and you couldn't do it.