please follow this
change _prepareCollection()
function with this
protected function _prepareCollection()
{
$collection = Mage::getResourceModel($this->_getCollectionClass());
$collection->getSelect()->join(array('invoice' => 'sales_flat_invoice'),
'invoice.entity_id = main_table.entity_id', null)
->columns('(invoice.grand_total - invoice.tax_amount) AS grand_excl_tax');
$this->setCollection($collection);
return parent::_prepareCollection();
}
<br>
and add Column in _prepareColumns() function
<br>
$this->addColumn('grand_excl_tax', array(
'header' => Mage::helper('customer')->__('GrandTotal(excl. tax)'),
'index' => 'grand_excl_tax',
'filter_condition_callback' => array($this, '_applyMyFilter'),
'type' => 'currency',
'align' => 'right',
'currency' => 'order_currency_code',
));
and add this _applyMyFilter
function for filter_condition_callback
protected function _applyMyFilter(Varien_Data_Collection_Db $collection, Mage_Adminhtml_Block_Widget_Grid_Column $column)
{
$select = $collection->getSelect();
$field = $column->getIndex();
$value = $column->getFilter()->getValue();
$select->where("invoice.grand_total - invoice.tax_amount>?", $value['from']);
$select->where("invoice.grand_total - invoice.tax_amount<?", $value['to']);
}