using phpExcel to read some cells

I'm trying to read some worksheets using a filter, but the problem is that I can't get the cell values, when those cells are using cells

  $objReader = PHPExcel_IOFactory::createReader('Excel5');
  $objReader->setLoadSheetsOnly('Data Sheet #1');

  $myFilter = new CellReadFilter(1, 7, range('A', 'F'));
  $objReader->setReadDataOnly(true);
  $objReader->setReadFilter($myFilter);

  $objPHPExcel = $objReader->load('sampleData/example1.xls');

  $loadedSheetNames = $objPHPExcel->getSheetNames();
  foreach ($loadedSheetNames as $sheetIndex => $loadedSheetName) {
     echo $sheetIndex, ' => ', $loadedSheetName, '<br />';
     $sheetData = $objPHPExcel->getActiveSheet()->toArray(null,true,true,true);
     var_dump($sheetData);
  }

My excel file, on the F1 cell, I use the following formula: =C2, but the output of my script says that F1 is null and not 23.45 as expected.

 0 => Data Sheet #1

 array (size=3)
   1 => 
array (size=6)
  'A' => string 'Integer Numbers' (length=15)
  'B' => float 123
  'C' => float 234
  'D' => float -345
  'E' => float 456
  'F' => null
  2 => 
array (size=6)
  'A' => string 'Floating Point Numbers' (length=22)
  'B' => float 1.23
  'C' => float 23.45
  'D' => float 3.45E-6
  'E' => float -45.678
  'F' => float 56.78
  3 => 
array (size=6)
  'A' => string 'Strings' (length=7)
  'B' => string 'Hello' (length=5)
  'C' => string 'World' (length=5)
  'D' => null
  'E' => string 'PHPExcel' (length=8)
  'F' => null

and my cell filter class looks like in the documentation sample:

class CellReadFilter implements PHPExcel_Reader_IReadFilter {

   private $_startRow = 0;
   private $_endRow = 0;
   private $_column = array();

   public function __construct($startRow, $endRow, $column) {
      $this->_startRow = $startRow;
      $this->_endRow = $endRow;
      $this->_column = array_merge($column, array('AA'));
   }

   public function readCell($column, $row, $worksheetName = '') {
      if ($row >= $this->_startRow && $row <= $this->_endRow) {
         if (in_array($column, $this->_column)) { return true; }
      }
      return false;
   }

}

Validation for you read filter, modify the readCell to test what criteria are being applied, and to identify which cells match the criteria and why they are being accepted/rejected:

public function readCell($column, $row, $worksheetName = '') {
    echo 'Testing worksheet ', $worksheetName, 'row ', $row, ' column ', $column, PHP_EOL;
    if ($row >= $this->_startRow && $row <= $this->_endRow) {
        'Cell is within row range',PHP_EOL;
        if (in_array($column, $this->_column)) { 
            'VALID: Cell is within column range',PHP_EOL;
            return true; 
        }
        'INVALID: Cell is outside column range',PHP_EOL;
    } else {
        'INVALID: Cell is outside row range',PHP_EOL;
    }
    return false;
}