Well then you would have to use the ChatWndReceiveMessage event and match the
Message with some string.
JScript code:
var greetings = [
"hi",
"hello",
"hey"
];
function OnEvent_ChatWndSendMessage(ChatWnd, Origin, Message){
if(Origin != Messenger.MyName) for(i in greetings) if(Message == greetings[i]) ChatWnd.SendMessage ("hi");
}