ExtJs Grid怎样合计列,取其他列的值

   1:  {

   2:     dataIndex : 'Price',

   3:     header : '金额',

   4:     hidden : false,

   5:     renderer : function (value, cellmeta, record, rowIndex, columnIndex, store) 

   6:    {

   7:           return record.data["Price"]*record.data["Amount"]

   8:    }

   9:  }