class PivotUtils {

    static Cell addCellValueTo(Cell source, Cell target){

        if (source == null) {
            return target;
        }

        if (target.getCellType()==CellType.NUMERIC && source.getCellType()==CellType.NUMERIC ){
            double val1 = target.getNumericCellValue();
            double val2 = source.getNumericCellValue();
            target.setCellValue(val1+val2);
        }

        return target;
    }

}