How to prevent any more keystrokes, or remove the last word entered

Hi, i'm looking to limit the number of words entered into the ckeditor. So far i have a simple way of counting the number of words, and updating a counter. But now i need to do something when the limit is reached, like remove the last word/letter entered, or prevent any more characters being entered:

CKEDITOR.on("instanceReady", function(e)
{
	var counterVal = Number($('.countdown-val').text());
	e.editor.on('change', function () {
    	var newVal = counterVal - $(e.editor.getData()).text().split(/\s/).length;
		$('.countdown-val').text(newVal);
		if(newVal<0) return false; // prevent keystroke here, unless it's delete
	});
});