code: function AddCallback(mesgId, callbackFunction, callbackTimeout) {
      var callbackElement, now;
  
      now = new Date().getTime();
  
      callbackElement = {
          id      :   mesgId,
          func    :   callbackFunction,
          timeout :   now + callbackTimeout
      };
  
      callbackList.push(callbackElement);
  }
docs: Add a callback for a specific message ID
  @param string mesgId
  @param function callbackFunction
  @param number callbackTimeout