Sure you can, using the OnEvent_MessageRecieved
something like
code:
if(Origin == Messenger.MyName) //Message is sent by you
{
if(Message == "Blah Blah")//replace "Blah Blah" with "Hello!"
{
return "Hello!";
}
}
unfortunately, the text you replace it with can't be any longer than what you actually send.
Not tested, but as far as I am aware, that is how this event works.