jquery after keyup event

I am using jQuery.autocomplete plugin. What i wants is if returned options are greater than 30 then wants to display some message like list is not complete. To handle this i did

$('div').ajaxStop(function() {
    if ($(this).find('DIV').length >= 30) {
        $开发者_如何学JAVA("<div class='autocomplete clsautocomplete' style='background-  color:#ffffb0'>Partial list - keep typing to filter</div>").insertAfter($(this));
    } else {
        $('.test').hide();
    }
});

and for next time it gets value form cache so the ajaxStop is not called.

thats why i am trying to check this on keyup event but it is not working.

If some has idea to handle this then please give to me.

Thanks