public function getHighestRowAndColumn()
    {
        // Lookup highest column and highest row
        $col = array('A' => '1A');
        $row = array(1);
        foreach ($this->getCellList() as $coord) {
            sscanf($coord, '%[A-Z]%d', $c, $r);
            $row[$r] = $r;
            $col[$c] = strlen($c).$c;
        }
        if (!empty($row)) {
            // Determine highest column and row
            $highestRow = max($row);
            $highestColumn = substr(max($col), 1);
        }

        return array(
            'row'    => $highestRow,
            'column' => $highestColumn
        );
    }