Adding grand total to jqgrid programatically

I'm learning how to use jQGrid and i'm trying to put the grand total at bottom of grid but I can't it just appears as a blank row.

Im trying to show the 'Report' column grand total, there is my code:

function FillReportsGrid(GridName, PagerName) {

    jQuery(GridName).GridUnload();
        $.ajax({
        url: '../ajaxwebservices/json.asmx/SearchMobileReport',
        dataType:'json',
        type:'POST',
        contentType: 'application/json; charset=utf-8',
        data: '{EmployeeID:\"' + $('#txtEmployeeID').val() + '\",Plant:\"' + $('#drplstPlant').val() + '\",Department:\"' + $('#开发者_运维技巧drplstDepartment').val() + '\",VendorName:\"' + $('#drplstVendorName').val() + '\",MobileNumber:\"' + $('#txtMobileNumber').val() + '\",InvoiceNumber:\"' + $('#txtInvoiceNumber').val() + '\",OrderBy:\"'+$('#ddlOrderBy').val()+'\",Month:\"'+$('#ddlMonth').val()+'\",Year:\"'+$('#ddlYear').val()+'\"}',
        success: function(msg) {
            var mydata = jQuery.parseJSON(msg);
            jQuery(GridName).jqGrid({
                datatype: "local",
                data: mydata,
                colNames: ['Bill #', 'MISC', 'Mobile #', 'Reporting', 'Invoice', 'Minutes', 'Comments', 'Cell Adj.', 'Data Adj.', 'Equip Adj.', 'Vendor Activity'],
                colModel:
                              [{ name: 'BillID', index: 'BillID', width: 20, sorttype: 'int', key: true },
                                { name: 'MISC', index: 'MISC', width: 40 },
                                { name: 'MobileNumber', index: 'MobileNumber', width: 40},
                                { name: 'VendorName', index: 'VendorName', width: 40},
                                { name: 'Reporting', index: 'Reporting', width: 40, align: 'right', summaryType: 'sum', sorttype: 'number', formatter: 'number', summaryTpl: '<b>{0}</b>' },
                                { name: 'Invoice', index: 'Invoice', width: 40, align: 'right' },
                                { name: 'Minutes', index: 'Minutes', width: 40},
                                { name: 'Comments', index: 'Comments', width: 40},
                                { name: 'CellAdjustment', index: 'CellAdjustment', width: 40, align: 'right' },
                                { name: 'DataAdjustment', index: 'DataAdjustment', width: 40, align: 'right'},
                                { name: 'EquipAdjustment', index: 'EquipAdjustment', width: 40, align: 'right'},
                                { name: 'VendorActivity', index: 'VendorActivity', width: 40}
                                 ],
                pager: jQuery(PagerName),
                rowNum: 25,
                rowList: [10, 25, 50],
                sortname: 'BillID',
                sortorder: 'desc',
                viewrecords: true,
                caption: '',
                autowidth: true,
                ignoreCase: true,
                height: "100%",
                footerrow: true,
                userDataOnFooter: true,
                grouping: true,
                groupingView : {
                    groupField: ['VendorName'],
                    groupColumnShow : [false],
                    groupText: ['<b>{0} - {1} Item(s)</b>'],
                    groupSummary : [true]
                }

            })
            jQuery(GridName).jqGrid('navGrid', PagerName, { edit: false, add: false, del: false, searchtext: 'Search', refreshtext: 'Reload' });
                jQuery(GridName).jqGrid('navButtonAdd', PagerName, { caption: "Add", title: "Add New User", buttonicon: 'ui-icon ui-icon-plus',
                    onClickButton: function() {
                    OpenAddNewItem();
                    }
                });
        }
    });
}

Thank you, I hope someone can help me, and sorry if my english is not very good.

Add the loadComplete event and use the getCol method to calculate the sum:

loadComplete: function () {

    var reportSum = jQuery(GridName).jqGrid('getCol', 'Reporting', false, 'sum');

    jQuery(GridName).jqGrid('footerData', 'set', 
    { 
        BillID: 'Total:',
        Reporting: reportSum 
    });
}

At the end I needed to add the loadComplete event and use the getCol method to calculate the sum at the bottom