use this _applyMyFilter function for filter_condition_callback

use 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']);
}

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();
         
    }


and add Column in _prepareColumns() function 



$this->addColumn('grand_excl_tax', array(
            'header'    => Mage::helper('customer')->__('GrandTotal(excl. tax)'),
            'index'     => 'grand_excl_tax',
            'filter_condition_callback' => array($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

use this _applyMyFilter function for filter_condition_callback