How do I prevent spam in a custom chat?

I have a fully functioning chat system, but how would I go about prevent sending messages after sending a certain amount within in an amount of time. It needs to be server side when the server sends the message to all players.

small example of something similar I made this on spot so prob errors:

local script

function onFocusLost(EnterPressed)
	if EnterPressed then
		if messageBox.Text ~= '' then
			event:FireServer(messageBox.Text)
end
end
end

server side

event:Connect(function(player, message)
filter stuff blah
allchat:FireAllClients(player.Name, message)
end)