docs: public int getRelativeSField(int iSFieldSeq)
      {
          Convert lastField = null;
          for (int i = 0; i < m_gridScreen.getSFieldCount(); i++)
          {
              Convert field = m_gridScreen.getSField(i).getConverter();
              if (field != null)
                  field = field.getField();
              if (m_gridScreen.getSField(i) instanceof ToolScreen)
                  field = null;
              
              if ((field != null) && (field != lastField))
                  iSFieldSeq--;       // Skip controls that belong to the previous field
              lastField = field;
              
              if (iSFieldSeq < 0)
                  return i;
          }
          return m_gridScreen.getSFieldCount() - 1;   // Never
      }