public function setFontForCellRange(PHPRtfLite_Font $font, $startRow, $startColumn, $endRow = null, $endColumn = null)
    {
        list($startRow, $startColumn, $endRow, $endColumn)
                = PHPRtfLite_Table::getValidCellRange($startRow, $startColumn, $endRow, $endColumn);

        if ($this->checkIfCellExists($startRow, $startColumn)
            && $this->checkIfCellExists($endRow, $endColumn))
        {
            $cells = $this->getCellsByCellRange($startRow, $startColumn, $endRow, $endColumn);
            foreach ($cells as $cell) {
                $cell->setFont($font);
            }
        }
    }