When someone talks to you, you can add the chatwnd object to an array, using the chatwnd's handle to identify it...
code:
var myArray = new Array();
function OnEvent_ChatWndRecieveMessage(ChatWnd, Origin, Message){
myArray[ChatWnd.Handle] = ChatWnd;
}
Then in your timer you can tell it to send a message to all the chatwnds in the array. Obviously, you will want to check that it's specific people unless you want it to send to everybody that sends you a message