How to specifically validate a certain form field using Jquery Validation plugin
<p>I'm using the <a href="http://bassistance.de/jquery-plugins/jquery-plugin-validation/" rel="nofollow">Jquery Validation plugin</a> to validate my form on the client before submitting.</p>

<p>There is a specific field in my form that I want to validate using ajax to the server, once the user has filled out that field (onblur). 
(Basically it's the username field, I want to check on the server if the username is available and show a message accordingly)</p>

<p>Here is the code I'm using to validate my form:</p>

<pre><code>$(document).ready(function()
{
     $("#signupForm").validate({
        submitHandler: ajaxSubmitForm});

});
</code></pre>

<p>(ajaxSubmitForm is just the js code that submits the form)</p>

<p>How can I use the Jquery Validation plugin to have the username field send its value to the server (using ajax) when it has changed and have the server return a result that somehow marks that field as valid on the client so the rest of the validation works?</p>

<p>Thanks</p>
