...
      spread.bind(GC.Spread.Sheets.Events.PivotTableChanged, function (evt, args) {
        var sheet = spread.getActiveSheet();
        var pt = sheet.pivotTables.get(args.pivotTableName);
        if (pt) {
          var sheetRow = sheet.getRowCount();
          var sheetCol = sheet.getColumnCount();
          var ptRange = pt.getRange();
          if (ptRange.content) {
            var ptRowCount = ptRange.content.row + ptRange.content.rowCount;
            sheet.setRowCount(Math.max(ptRowCount, sheetRow));
            var ptColCount = ptRange.content.col + ptRange.content.colCount;
            sheet.setColumnCount(Math.max(ptColCount, sheetCol));
          }
        }
      });

...