A Proper Event Countdown

Hey guys,
I'm trying to utilize events to create a proper countdown event when I have a list of players ready to start the game. Problem is the main check for readiness is in Update() and my countdown is a coroutine thus I always end up flooding the network with timeLeft messages. Is there a better approach here ?

public IEnumerator CheckLobbyPlayersReady()
        {
            int ready = 0;
            foreach (PlayerListItem p in lobbyPlayers)
                if (p.isReady)
                    ready++;

            if (ready == lobbyPlayers.Count)
            {
                yield return new WaitForSeconds(1);
                countdown.TimeLeft = countDownTime--;
                countdown.Send();
            }

         //if time is up,  start game
}