Exception in thread "main" org.apache.poi.ss.formula.FormulaParseException: Specified named range 'RtSummary.1' does not exist in the current workbook.

//cell 3 (total orders) will be filled later
    String summarySheetName="RtSummary."+snapshots[i].trim()+Integer.toString(i+1);
    String detailSheetName="RtDetail."+snapshots[i]+(i+1);
    Row orderRow;


    //first comparison table content
    int rowOffset=15+snapshots.length;
    curRow=overviewSheet.createRow(rowOffset+i);
    orderRow=curRow;
    curCell=curRow.createCell(1);
    curCell.setCellStyle(lrBarStyle);
    curCell.setCellValue(snapshots[i]);

    curCell=curRow.createCell(2);
    curCell.setCellStyle(lrBarStyle);
    if(sameDay)
        curCell.setCellValue(dateSDF.format(startDate.getTime()));
    else
        curCell.setCellValue(dateSDF.format(startDate.getTime())+"-"+dateSDF.format(endDate.getTime()));

    curCell=curRow.createCell(4);
    curCell.setCellStyle(lrBarStyle);
    System.out.println(summarySheetName);
    curCell.setCellFormula(summarySheetName+"!N"+(routes.length+2));
    System.out.println("0k");