It can be done, but you have to tell us how you are determining if the mIRC user is in the game or not. Is it stored somewhere?
If i understand correctly, the message will be sent by the people who has the script in remote. The user ingame who can use it is done by !setuser <nick> or something?
So if I did !setuser FriLLeT and then go ingame with the name 'FriLLeT' i would be able to use it and send this
@ being the ingame admin chat command.
You can see in the screenshots in the original topic how the server messages are sent.
PS: late reply, internet troubles