If you want to set a word count limit on your event description then you could try this approach. It will only work with JCE or TinyMCE editors.
Using the template override for editing events described here you should use this sample file.
The basic idea is to use this piece of code
$toomanywords = JText::_("Too many words - please reduce the length of your description",true);
$script = <<<SCRIPT
var maxwords = 6;
var lastwordcount = 0;
function jevedchanged(doalert){
var strip = (tinyMCE.editors.jevcontent.getContent()).replace(/(<([^>]+)>)/ig,"");
strip = strip.replace(/^\s+|\s+$/g, '');
var wordcount = strip.split(' ').length;
if (wordcount==0 && strip.length>0) wordcount=1;
var text = wordcount + " Words, " + strip.length + " Characters"
tinymce.DOM.setHTML(tinymce.DOM.get(tinyMCE.editors.jevcontent.id + '_path_row'), text);
//tinyMCE.editors.jevcontent.win.focus();
if (wordcount>maxwords && (wordcount!=lastwordcount || doalert) ) {
lastwordcount = wordcount;
alert('$toomanywords');
}
if (wordcount>maxwords) return false;
return true;
}
window.addEvent('load',function(){
if (tinyMCE && tinyMCE.editors.jevcontent) {
jevedchanged(false);
tinyMCE.editors.jevcontent.onKeyUp.add(function(ed, l) { jevedchanged(false);});
tinyMCE.editors.jevcontent.onPaste.add(function(ed, l) { jevedchanged(false);});
}
});
SCRIPT;
$document = JFactory::getDocument();
$document->addScriptDeclaration($script);
In this case we have a word limit of 6 (rather small I agree) and a warning message that says "Too many words - please reduce the length of your description". Change these to what you want.