<script type="text/javascript">
        var spConfig = new Product.Config(<?php echo $this->getJsonConfig() ?>);
        document.observe("dom:loaded", function() {
            var customValidation = false;
            var priceFormat = <?php echo $this->helper('tax')->getPriceFormat(); ?>;
            $$('.validate-custom-configurable').each(function(el){
                el.observe('click',function(event){
                    var total_amount = optionsPrice.productPrice;
                    $$('label.label-radio-configurable input').each(function(elmn){
                        if ( elmn.checked == true ) {
                            total_amount = total_amount + parseFloat(elmn.parentNode.id);
                        }
                    });
                    $$('.price').each(function(priceobj) {
                        priceobj.update(formatCurrency(parseFloat(total_amount), priceFormat)).innerHTML;
                    });
                });
            });
            Validation.addAllThese([
                ['validate-custom-configurable', 'This is a required field.', function(v) {
                    $$('.validate-custom-configurable').each(function(el){
                        if (el.checked) {
                            customValidation = true;
                        }
                    });
                    return customValidation;
                }]
            ]);
        });
    </script>