public function setFormula($cellName, $formula)
    {
        if ($cellName == '')
            throw new Exception('Cell Name not specified');
        
        if ($formula == '')
            throw new Exception('Formula not specified');
        
        //Build URI
        $strURI = Product::$baseProductUri . '/cells/' . $this->getFileName() . '/worksheets/' . $this->worksheetName . 
                  '/cells/' . $cellName . '?formula=' . $formula;
        //Sign URI
        $signedURI = Utils::sign($strURI);
        
        //Send request and receive response
        $response = Utils::processCommand($signedURI, 'POST', '', '');
        $json = json_decode($response);
        if ($json->Code == 200)
            return $json->Cell;
        else
            return false;
    }