gistfile1.txt

<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to [email protected] so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magento.com for more information.
 *
 * @category    Varien
 * @package     Varien_Data
 * @copyright  Copyright (c) 2006-2015 X.commerce, Inc. (http://www.magento.com)
 * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */

/**
 * Form text element
 *
 * @category   Varien
 * @package    Varien_Data
 * @author      Magento Core Team <[email protected]>
 */
class Varien_Data_Form_Element_YourCustomFormElement extends Varien_Data_Form_Element_Text
{
    public function __construct($attributes=array())
    {
        parent::__construct($attributes);
        $this->setType('text');
        $this->setExtType('textfield');
    }

    public function getHtml()
    {
        $this->addClass('input-text');

        $value = $this->getEscapedValue();

        if (empty($value))
        {
            $value="your custom dynamic content";

            $this->setData('value', $value);

            $html = parent::getHtml();

        }

        return $html;
    }

    public function getHtmlAttributes()
    {
        return array('type', 'title', 'class', 'style', 'onclick', 'onchange', 'onkeyup', 'disabled', 'readonly', 'maxlength', 'tabindex');
    }
}