public function formatColumn($column, $format_code)
    {

        // By default we'll use USD.
        $format_code = isset($format_code) ? $format_code : 'USD';
        $phpexcel_format = \PHPExcel_Style_NumberFormat::FORMAT_CURRENCY_USD_SIMPLE;

        // Map to specific formats in PHPExcel
        if ($format_code === 'USD') {
            $phpexcel_format = \PHPExcel_Style_NumberFormat::FORMAT_CURRENCY_USD_SIMPLE;
        }
        elseif ($format_code === \PHPExcel_Style_NumberFormat::FORMAT_CURRENCY_USD_SIMPLE) {
            $format_code = 'USD';
        }

        $columns = $this->getPHPExcelColumns();
        if (!array_key_exists($column, $columns)) {
            return;
        }
        $phpexcel_column = $columns[$column];
        $page = $this->excel->getActiveSheet();
        foreach ($page->getRowIterator() as $row) {
            $row_index = $row->getRowIndex();
            $page->getStyle("$phpexcel_column$row_index")
                 ->getNumberFormat()
                 ->setFormatCode($phpexcel_format);
        }

        return parent::formatColumn($column, $format_code);
    }