middlename field to billing address

<?php $middleName = $this->getLayout()->createBlock('customer/widget_name')
    ->setObject($this->getQuote()->getBillingAddress())
    ->setFieldIdFormat('billing:%s')
    ->setFieldNameFormat('billing[%s]')
?>

<?php if ($middleName->showMiddlename()): ?>
<?php $isMiddlenameRequired = $middleName->isMiddlenameRequired(); ?>
    <div class="field name-middlename" style="display: none">
        <label for="<?php echo $middleName->getFieldId('middlename')?>"<?php echo $isMiddlenameRequired ? ' class="required"' : '' ?>><?php echo $isMiddlenameRequired ? '<em>*</em>' : '' ?><?php echo $middleName->getStoreLabel('middlename') ?></label>
        <div class="input-box">
            <input type="text" id="<?php echo $middleName->getFieldId('middlename')?>" name="<?php echo $middleName->getFieldName('middlename')?>" value="<?php echo $middleName->escapeHtml($middleName->getObject()->getMiddlename()) ?>" title="<?php echo Mage::helper('core')->quoteEscape($middleName->getStoreLabel('middlename')) ?>" class="input-text <?php echo $middleName->helper('customer/address')->getAttributeValidationClass('middlename') ?>" <?php echo $middleName->getFieldParams() ?> />
        </div>
    </div>

    <script>
    Event.observe(window, 'load', function() {
        var mname = $$('.name-middlename').first();
        var fname = $$('.input-firstname').first();
        if(mname){
            fname.insert({after: mname});
            mname.show();
        }
    });
    </script>
<?php endif; ?>