Now i'm trying to use the poi library. Like the following example... the lib is also installed with mendix.
HSSFWorkbook wb = new HSSFWorkbook(); HSSFSheet sheet = wb.createSheet("Facturatie");
    HSSFRow row = sheet.createRow((short)0);
    row.createCell((short)0).setCellValue("Datum gereed");
    row.createCell((short)1).setCellValue("Nummer");
    row.createCell((short)1).setCellValue("Totaalprijs");
    int rowNumber = 1;
    for (Order order: this.ordersTeFactureren){
        row = sheet.createRow((short)rowNumber);
        row.createCell((short)0).setCellValue(order.getDatumGereed());
        row.createCell((short)0).setCellValue(order.getNummer());
        row.createCell((short)0).setCellValue(order.getTotaalPrijs());
        rowNumber++;
    }