jQuery Grid Plugin - jqGrid

I'm a newbie to jqgrid. This is what I'm planning to do....

I have a working jqgrid with all the data . When a user clicks on a row, I want to show additional details for that row , all the data for the details are in the gris as hidden .

My question is how do I retrieve the data for that particular row which is hidden in the parent grid. I was using "+$("#grid").getCell (postdata, 'deviceName') , but of no use...

Here is my code

    <script type='text/javascript'>
    $(function() {
        $("#grid").jqGrid({
               url:'${recordsUrl}',
            datatype: 'json',
            mtype: 'GET',
               colNames:['serverId', 'deviceName', 'businessUnit'],
               colModel:[
                   {name:'serverId',index:'serverId', width:100, editable:true, editrules:{required:true}, editoptions:{size:10}},
                   {name:'deviceName',index:'deviceName', width:100, editable:true, editrules:{required:true}, editoptions:{size:10}},
                   {name:'businessUnit',index:'businessUnit', width:50, editable:true, editrules:{required:true}, editoptions:{size:10}}
               ],
               postData: {},
            rowNum:10,
               rowList:[10,20,40,60],
               height: 240,
               autowidth: true,
            rownumbers: true,
               pager: '#pager',
               sortname: 'serverId',
            viewrecords: true,
            sortorder: "asc",
            caption:"Records",
            subGrid: true,
            
            subGridRowExpanded: function(subgrid_id, row_id) {
                var html = "<span>ZZ19 Some HTML text which corresponds the row with id="+$("#grid").getCell (postdata, 'deviceName')+
                           row_id + " xxy </span><br/>";
         
                $("#" + subgrid_id).append(html);
            },
            emptyrecords: "Empty records",
            loadonce: true,
            loadComplete: function() {},
            jsonReader : {
                root: "rows",
                page: "page",
                total: "total",
                records: "records",
                repeatitems: false,
                cell: "cell",
                id: "serverId"
            }
        });