code: protected PrefixSuffix interpretPageNo(BandElement bandElement) {
      	String exp = "";
  		try {
  			String pattern = "";
  			if (bandElement instanceof FieldBandElement) {
  				pattern = ((FieldBandElement)bandElement).getPattern();
  			}
  			exp = StringUtil.getValueAsString( evaluateExpression(((ExpressionBandElement) bandElement), "", null), pattern);
  			String name = "$V_" + Variable.PAGE_NO_VARIABLE;
  			return StringUtil.parse(exp, name);
  		} catch (QueryException ex) {
  			ex.printStackTrace();
  		}
  		return null;
      }
docs: for exporters who need to replace PAGE_NO variable (RTF, XLS)