Magento 1. Add custom Textfield with dynamic content in system.xml

If you want to add a custom textfield with dynamic content instead of static content from config.xml you can simply add your own data form element like this

place following class under
app\code\local\Varien\Data\Form\Element\YourCustomTextElement.php



At next you can use your custom form element in system.xml of your module like this. Place your new configvariable in your target field group