PHPExcel: formula error (IF)

I'm trying to insert this formula

=IF(Datenbasis!B3<0;((Datenbasis!K3-Datenbasis!B3)/ABS(Datenbasis!B3))^(1/9)-1;(Datenbasis!$K$3/Datenbasis!$B$3)^(1/9)-1)

into this samplefile1 with this code:

// ....
try
{
    $inputFileType = PHPExcel_IOFactory::identify("phpexceltest.xls");
    $objReader = PHPExcel_IOFactory::createReader($inputFileType);
    $objPHPExcel = $objReader->load("phpexceltest.xls");
}
catch(Exception $e)
{
    $_loadingerror = TRUE;
}
if ($_loadingerror === TRUE)
{
   // Fehler beim Laden der Vorlagen-Datei!
   die("Fehler!");
}
$objPHPExcel->setActiveSheetIndex("0");
// ....
$objPHPExcel->getActiveSheet()->setCellValue("J4", "=IF(Datenbasis!B3<0;((Datenbasis!K3-Datenbasis!B3)/ABS(Datenbasis!B3))^(1/9)-1;(Datenbasis!$" . "K$3/Datenbasis!$" . "B$3)^(1/9)-1)");
// ....
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
$objWriter->save("ready.xls");

I get this error

Fatal error: Uncaught exception 'Exception' with message 'Results!J4 -> undefined variable ';'' in ...\PHPExcel\Cell.php:288 Stack trace: #0 ...\PHPExcel\Writer\Excel5\Worksheet.php(441): PHPExcel_Cell->getCalculatedValue() #1 ...\PHPExcel\Writer\Excel5.php(171): PHPExcel_Writer_Excel5_Worksheet->close() #2 phpexceltest.php(446): PHPExcel_Writer_Excel5->save('ready.xls') #3 {main} thrown in ...\PHPExcel\Cell.php on line 288

and I have no idea why. When I use this formula in Excel directly, it's working.

Any ideas, what to do?