Disable button unless bot selectors have value
<p>OK, I have two HTML select elements and a button. I need to disable the button unless <strong>both</strong> of the selectors have any but default (na) values.</p>

<p>I've got this so far, but it doesn't really work. What am I missing? </p>

<p><strong>JS</strong></p>

<pre><code>function toggleBtn() {
    if($(".mySelect").val() == "na") {
        $(this).parents("td").find("input:button").attr("disabled", "disabled");    
    } else {
        $(this).parents("td").find("input:button").attr("disabled", "");    
    }
});

toggleBtn();

$(".mySelect").change(toggleBtn());
</code></pre>

<p><strong>HTML</strong></p>

<pre><code>&lt;table&gt;
&lt;tr&gt;
  &lt;td&gt;
    &lt;select class="mySelect"&gt;
      &lt;option value="na"&gt;&lt;/option&gt;
      &lt;option value="1"&gt;value 1&lt;/option&gt;
      &lt;option value="2"&gt;value 2&lt;/option&gt;
    &lt;/select&gt; 

    &lt;select class="mySelect"&gt;
      &lt;option value="na"&gt;&lt;/option&gt;
      &lt;option value="3"&gt;value 3&lt;/option&gt;
      &lt;option value="4"&gt;value 4&lt;/option&gt;
    &lt;/select&gt; 
  &lt;/td&gt;
&lt;/tr&gt;
&lt;tr&gt;
  &lt;td&gt;
    &lt;input type="button" value="click me"&gt;
  &lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;
</code></pre>
