private void cleanBeforeMergeOnValidCells(XSSFSheet sheet,CellRangeAddress region, XSSFCellStyle cellStyle )
{
    for(int rowNum =region.getFirstRow();rowNum<=region.getLastRow();rowNum++){
        XSSFRow row= sheet.getRow(rowNum);
        if(row==null){
            sheet.createRow(rowNum);
            logger.trace("while check row "+rowNum+" was created");
        }
        for(int colNum=region.getFirstColumn();colNum<=region.getLastColumn();colNum++){
            XSSFCell currentCell = row.getCell(colNum); 
           if(currentCell==null){
               currentCell = row.createCell(colNum);
               logger.trace("while check cell "+rowNum+":"+colNum+" was created");
           }    

           currentCell.setCellStyle(cellStyle);

        }
    }


}