[jQuery] [Validation plugin] attaching onclick validation to checkboxes before submit button is clicked?

[w1ntermut3]

Using the Validation plugin (http://docs.jquery.com/Plugins/
Validation/)

I've got checkboxes like this:

<input type="checkbox" name="q4" id="q4" value="1" />
<input type="checkbox" name="q4" id="q4" value="2" />
<input type="checkbox" name="q4" id="q4" value="3" />
<input type="checkbox" name="q4" id="q4" value="4" />
<input type="checkbox" name="q4" id="q4" value="5" />

and the following code making sure that only 3 can be chosen:

$(document).ready(function() {
        $('#fQuestionnaire1').validate({
                rules: {
                        q4: {
                                required: true,
                                maxlength: 3
                        }
                }
        });
});

This sort of works fine - when I click the form's Submit button, the
error message is displayed if more than three are selected. And from
then on,  the error message is toggled on and off by my ticking the
required number of boxes. But - and here's my question - I want that
behaviour BEFORE I've hit "Submit". As soon as I click that 4th
checkbox, I want the error message to appear. Currently it's happy to
let me select 4 items and then gives me the message when I hit
"Submit".

I notice that the docs for the validate() "onfocusout" option - which
defaults to true - says "Validate elements (except checkboxes/radio
buttons) on blur." Why are they excluded? It's clearly possible to do,
because it does validate onblur AFTER the submit button has fired
once. Is this work-aroundable? Am I missing something important?

Thanks :)