If you can read the cell value you can then just pass it on to the PHP function strpos().
Example:
Example:
$objPHPExcel = $objReader->load('example.xlsx');
$sheet = $objPHPExcel->getActiveSheet();
$cell = $sheet->getCellByColumnAndRow(3,3);
if (strpos($cell->getValue(), 'Remote Operating system:') !== false) {
// Found text in cell now do something.
}