how to add new filter magento admin order filter by country

magento admin order filter by country

please give me php code for magento

C:\xampp\htdocs\m\app\code\local\Pkmodule\Reward\Block\Adminhtml\Reward\Grid.php

<?php class Pkmodule_Reward_Block_Adminhtml_Reward_Grid extends Mage_Adminhtml_Block_Widget_Grid { public function __construct() { parent::__construct(); $this->setId("rewardGrid"); $this->setDefaultSort("id"); $this->setDefaultDir("ASC"); $this->setSaveParametersInSession(true); } protected function _prepareCollection() { $collection = Mage::getModel("reward/reward")->getCollection(); $this->setCollection($collection); return parent::_prepareCollection(); } protected function _prepareColumns() { $groups = array("value","puneet","kumar"); $this->addColumn("id", array( "header" => Mage::helper("reward")->__("ID"), "align" =>"right", "width" => "50px", "type" => "number", "index" => "id", )); $this->addColumn("name", array( "header" => Mage::helper("reward")->__("NAME"), "align" =>"left", "width" => "50px", "type" => "options", 'options' => $groups, "index" => "name", )); $this->addColumn("order", array( "header" => Mage::helper("reward")->__("order"), "align" =>"left", "width" => "50px", "type" => "options", 'options' => $groups, "index" => "order", )); $this->addRssList('reward/adminhtml_rss_rss/reward', Mage::helper('reward')->__('RSS')); $this->addExportType('*/*/exportCsv', Mage::helper('sales')->__('CSV')); $this->addExportType('*/*/exportExcel', Mage::helper('sales')->__('Excel')); return parent::_prepareColumns(); } public function getRowUrl($row) { return $this->getUrl("*/*/edit", array("id" => $row->getId())); } protected function _prepareMassaction() { $this->setMassactionIdField('id'); $this->getMassactionBlock()->setFormFieldName('ids'); $this->getMassactionBlock()->setUseSelectAll(true); $this->getMassactionBlock()->addItem('remove_reward', array( 'label'=> Mage::helper('reward')->__('Remove Reward'), 'url' => $this->getUrl('*/adminhtml_reward/massRemove'), 'confirm' => Mage::helper('reward')->__('Are you sure?') )); return $this; } }

magen i add new $this->addColumn for filter but value not showing ?