jQuery Grid Plugin - jqGrid

Someone please help the newby with a problem.  I am using version 3.4.2 in a Windows environment. 

I have a grid as a subgrid.  I am trying to read data from the subgrid in the function for the subGridRowExpanded event.  getRowData and getCell come back with undefined values.  This logic works fine if it is a click function external to the subgrid but not in the subGridRowExpanded event.

What am I missing here? Code below.

Thanks,

Jerry

jQuery("#list").jqGrid({
   url:'cem_db_if.php?q=1',
   colNames:['Cemetery','USGS GNIS ID', 'County','USGS map','Location'],
   colModel :[
     {name:'cem_name', index:'cem_name', width:200, align:'center'},
     {name:'cem_usgs', index:'cem_usgs', width:100, align:'center'},
     {name:'cem_county_name', index:'cem_county_name', width:100, align:'center' },
     {name:'cem_map', index:'cem_map', width:100, align:'center'},
     {name:'cem_description_short', index:'cem_description_short', width:400, align:'center'} ],
   height:'auto',
   pager: '#pager',
   rowNum:15,
   rowList:[15,30,60],
   sortname: 'cem_name',
   sortorder: "asc",
   mtype: 'POST',
   postData:{table_name:"DT_Cemetery"},   
   viewrecords: true,
   imgpath: 'themes/basic/images',
   caption: 'TNGenWeb Cemetery Database - Cemeteries',
   shrinkToFit: 'true',
   width:880,
   subGrid:'true',
   subGridRowExpanded: function(subgrid_id, row_id) {
    var subgrid_table_id;
    subgrid_table_id = subgrid_id+"_t";
     jQuery("#"+subgrid_id).html("<table id='"+subgrid_table_id+"' class='scroll'></table>");
     jQuery("#"+subgrid_table_id).jqGrid({
      url:"cem_db_if.php?q=3&id="+row_id,
      datatype: "xml",
      colNames: ['Cemetery detail',''],
      colModel: [
       {name:"item",width:150, align:'right'},
       {name:"prop",width:200, align:'left'}],
      height:'auto',
      rowNum:20,
      imgpath: 'themes/basic/images'
     });//end subgrid
          
     //get latitude from subgrid to draw google map
     alert("#"+subgrid_table_id);
     var lat = jQuery("#"+subgrid_table_id).getRowData(6);
     alert("item="+lat.item+" prop="+lat.prop+"...");

    }//end function
  }).navGrid('#pager',{edit:false,add:false,del:false})