Formatear celdas en Flexigrid

$(".flexme5").flexigrid({
                title: 'Overview by category', 
                url: 'PnLCalculations.asmx/GetRowData2',
                dataType: 'json',
                method: 'post',
                params: [{ name: 'uid', value: '<%= cSession.UserWeb %>' },
                         { name: 'entityId', value: '<%= cSession.EntityCode %>' },
                         { name: 'period', value: '<%= ddlPeriod.Text %>' },
                         { name: 'secondGroupOrder', value: 'Category' }
                         ],
                colModel: [
                { display: 'Folders Shortname', name: 'col01', width: 100, sortable: true, draggable: false, align: 'left' },
                { display: 'Category', name: 'col02', width: 100, sortable: true, draggable: false, align: 'left' },
                { display: 'Sum', name: 'col03', width: 100, sortable: true, draggable: false, align: 'right' },
                { display: 'Count', name: 'col04', width: 100, sortable: true, draggable: false, align: 'right' }
                ],
                sortname: "row01",
                sortorder: "asc",
                usepager: true,
                autoload: true,
                resizable: false,
                singleSelect: true,
                useRp: false,
                rp: 25,
                width: twidth,
                height: 505,
                preProcess: function(data) {
                    $.each(data.rows, function(i, row) {
                       if (parseInt(row.col03)<0) {
                          row.col03='
'+row.col03+'
';
                       }
                       if (parseInt(row.col03)>0) {
                          row.col03='
'+row.col03+'
';
                       }
                    });
                    return data;
                },
            });