docs: public int doMergeData(Object objData)
      {
          double dOrigData = ((Double)this.getOriginalData()).doubleValue();
          double dMergeData = ((Double)objData).doubleValue();
          double dCurrentData = this.getOwner().getValue();
          double dMergeAmount = dMergeData - dOrigData;
          double dNewAmount = dCurrentData + dMergeAmount;
          objData = new Double(dNewAmount);
          this.setOriginalData(new Double(dCurrentData));  // Just in case I come through here again
  
          return super.doMergeData(objData);
      }