Disable the checkbox of easyui datagrid

1. When the onLoadSuccess method of datagrid

datagrid({onLoadSuccess:function(data){
   var result = data.rows;
    for(var i=0; i<result.length; i++){
         var row = result[i] ;
         if(row.rowspan >1){
             $('#productGrid').datagrid('mergeCells',{
                 index:i,
                 field:'cpName',
                 rowspan:row.rowspan
             });
             $('#productGrid').datagrid('mergeCells',{
                 index:i,
                 field:'cpId',
                 rowspan:row.rowspan
             });
             $('#productGrid').datagrid('mergeCells',{
                 index:i,
                 field:'cpLogo',
                 rowspan:row.rowspan
             });
             i= i+row.rowspan;
         }
         if(row.pricePkgId == undefined || row.pricePkgId == null) {
             $(".datagrid-row[datagrid-row-index=" + i + "] input[type='checkbox']")[0].disabled = true;
         }
    }
}})