Programatically select jQueryUI Selectables

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.16/themes/base/jquery-ui.css">
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.17/jquery-ui.min.js"></script>
<form>
  <div class='myBoxes'>

    <label>Check 1<input type="checkbox" id="chk1" /> </label>
    <label>Check 2<input type="checkbox" id="chk2" /> </label>
    <label>Check 3<input type="checkbox" id="chk3" /> </label>
    <label>Check 4<input type="checkbox" id="chk4" /> </label>

  </div>
</form>

CSS

label {
  display: block;
  padding: 7px;
  width: 120px;
  margin-bottom: 14px;
  border: 1px solid red;
}

label.ui-selecting {
  background: lightgreen;
}

.LabelHighlight {
  background: lightgreen;
}

JavaScript

$(".myBoxes").selectable({

  filter: 'label',

  stop: function() {
    $(".ui-selected input", this).each(function() {
      this.checked = !this.checked;

      if ($(this).is(':checked')) {
        console.log($(this));
        $(this).parent().addClass("LabelHighlight")
      } else {
        $(this).parent().removeClass("LabelHighlight")
      }

    });
  }
});