The class that handles that button is Mage_Adminhtml_Block_System_Config_Form_Field_Export
. and it has the url in one of the methods, so you cannot use <frontend_type>export</frontend_type>
for your custom button. You have to create a new field renderer similar to Mage_Adminhtml_Block_System_Config_Form_Field_Export
and add your url in there.
Try it like this:
<?php
class [Namespace]_[Module]_Block_Adminhtml_System_Config_Custombutton extends Mage_Adminhtml_Block_System_Config_Form_Field implements Varien_Data_Form_Element_Renderer_Interface{
protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
{
$buttonBlock = Mage::app()->getLayout()->createBlock('adminhtml/widget_button');
$params = array(
'website' => $buttonBlock->getRequest()->getParam('website')
);
$data = array(
'label' => Mage::helper('adminhtml')->__('Do Something'),
'onclick' => 'setLocation(\''.Mage::helper('adminhtml')->getUrl("*/controller/action", $params) . '\' )',
'class' => '',
);
$html = $buttonBlock->setData($data)->toHtml();
return $html;
}
}
and your system.xml section should look like this
<export translate="label">
<label>Some button</label>
<sort_order>1</sort_order>
<type>button</type>
<show_in_default>1</show_in_default>
<show_in_website>1</show_in_website>
<show_in_store>1</show_in_store>
<frontend_model>[module]/adminhtml_system_config_custombutton</frontend_model>
</export>