Well - there is documentation for this.

You will need to use serializeCellData .

You may need to look at this docs here

Regards

is this posible?

MY source code:

 $("#tb_conf_servicios").jqGrid({url: 'configuracion/conf_servicios/lista.php',
            datatype: "xml",
            colNames: ['id', 'CUP', 'Descripción', 'Nivel','Plano', 'Sexo', 'Edad Inicio', 'Edad Fin'],
            colModel: [
                {name: 'id_serv', index: 'id_serv', width: 50, sortable: true, hidden: true},
                {name: 'cup', index: 'cup', width: 80, sortable: true},
                {name: 'descripcion', index: 'descripcion', width: 420, sortable: true},
                {name: 'nivel', index: 'nivel', width: 30, sortable: true, editable: true, edittype: 'select', editoptions: {value: "1:1;2:2;3:3;4:4"}},
                {name: 'plano', index: 'plano', width: 50, sortable: true, editable: true, edittype: 'select', editoptions: {value: "1:AC;3:AP;4:OT"}},
                {name: 'sexo', index: 'sexo', width: 30, sortable: true, editable: true, edittype: 'select', editoptions: {value: "A:A;M:M;F:F"}},
                {name: 'edad_inicio', index: 'edad_inicio', width: 65, sortable: true, editable: true},
                {name: 'edad_fin', index: 'edad_fin', width: 70, sortable: true, editable: true}],
            rowNum: 10,
            rowList: [10, 20, 30],
            pager: '#paginador_conf_servcios',
            sortname: 'id_serv',
            viewrecords: true,
            sortorder: "asc",
            xmlReader: {root: "rows",
                row: "row",
                repeatitems: true,
                id: "[id]"
            },
            caption: "Clasificacion de Servicios",
            height: '100%',
            cellurl: 'configuracion/conf_servicios/editar.php',
            beforeSubmitCell:function(id){
                var ret = $('#tb_conf_servicios').jqGrid('getRowData', id);
                alert(ret.nivel);
                $("#tb_conf_servicios").jqGrid('setPostData',{param2:"p2"});
            }
        });