public function unmergeCells($pRange = 'A1:A1')
    {
        // Uppercase coordinate
        $pRange = strtoupper($pRange);

        if (strpos($pRange, ':') !== false) {
            if (isset($this->mergeCells[$pRange])) {
                unset($this->mergeCells[$pRange]);
            } else {
                throw new PHPExcel_Exception('Cell range ' . $pRange . ' not known as merged.');
            }
        } else {
            throw new PHPExcel_Exception('Merge can only be removed from a range of cells.');
        }

        return $this;
    }