jQuery("#t_listadoGrid").append("<input type='button' value='Acciones' style='height:20px;font-size:-3'/>");
     jQuery("input","#t_listadoGrid").click(function(){
      alert("a ver que tal");
      var idSel = jQuery("#listadoGrid").jqGrid('getGridParam','selrow');
      if (idSel != null)
      {
       alert('fila seleccionada'+idSel);
      }
     });

and no at the beginning.

Regards,

...

jQuery("#t_listadoGrid").append("<input type='button' value='Acciones' style='height:20px;font-size:-3'/>");
     jQuery("input","#t_listadoGrid").click(function(){
      alert("a ver que tal");
      var idSel = jQuery("#listadoGrid").jqGrid('getGridParam','selrow');
      if (idSel != null)
      {
       alert('fila seleccionada'+idSel);
      }
     });
        
     jQuery("#listadoGrid").jqGrid({
         url:'/AODB2/realTime/arrivalFlight/NewArrivalFlight.action?accion=listar&selectedPage='+paginaSeleccionada,
      datatype: "json",
         colNames:[ "<s:text name=""/>",
            "<s:text name="iataCompanyCodeFieldArrivalFlight"/>","<s:text name="flightNumberFieldArrivalFlight"/>",
            "<s:text name="tailNumberFieldArrivalFlight"/>","<s:text name="joinedFieldArrivalFlight"/>",
            "<s:text name="runwayCodeFieldArrivalFlight"/>","<s:text name="statusCodeFieldArrivalFlight"/>",
            "<s:text name="arrivalSituationFieldArrivalFlight"/>","<s:text name="flightTypeCodeFieldArrivalFlight"/>",
            "<s:text name="airportArrivalCodeFieldArrivalFlight"/>","<s:text name="scheduledTimeFieldArrivalFlight"/>",
            "<s:text name="estimatedTimeFieldArrivalFlight"/>"
          ],
         colModel:[
        {name:'idArrivalFlight',index:'idArrivalFlight', width:5, align:'center', hidden:true},
           {name:'iataCompanyCode',index:'iataCompanyCode', width:140, align:'center', sortable: false, editable:true, editrules:{required:true},formoptions:{elmprefix:"(*)"}}, //editable:true sirve para que salga en las ventanas emergentes edit y add
           {name:'flightNumber',index:'flightNumber', width:140, align:'center', sortable:false, editable:true, editoptions:{size:40},editrules:{required:true},formoptions:{ elmprefix:"(*)"}}, //editrules para validaciones
           {name:'tailNumber',index:'tailNumber', width:140, align:'center', editable:true, sortable:false},
           {name:'joined',index:'joined', width:140, align:'center',editable:true, sortable:false,editrules:{required:true},formoptions:{ elmprefix:"(*)"},
            edittype: 'select', editoptions: { //transforma un campo normal en otro de tipo select
                               value: objJoined,  //lista para el select
                               dataInit: function (elem) {
                                       var v = $(elem).val(); //valor que se muestra por defecto
                               }
                       }
           },
           {name:'runwayCode',index:'runwayCode', width:140, align:'center', editable:true, sortable:false},
           {name:'statusCode',index:'statusCode', width:140, align:'center', editable:true, editoptions:{readonly:true}, sortable:false},
           {name:'situationName',index:'situationName', width:140, align:'center', editable:true, editoptions:{readonly:true}, sortable:false},
           {name:'flightTypeCode',index:'flightTypeCode', width:140, align:'center', editable:true,  sortable:false,
            edittype: 'select', editoptions: { //transforma un campo normal en otro de tipo select
                             value: objFlightType,  //lista para el select
                             dataInit: function (elem) {
                                     var v = $(elem).val(); //valor que se muestra por defecto
                               }
                       }
           },
           {name:'airportArrivalCode',index:'airportArrivalCode', width:140, align:'center', editable:true, editoptions:{readonly:true}, sortable:false},
           {name:'scheduledTime',index:'scheduledTime', width:140, align:'center', editable:true, editoptions:{readonly:true}, sortable:false},
           {name:'estimatedTime',index:'estimatedTime', width:140, align:'center', editable:true, editoptions:{readonly:true}, sortable:false}           
      ],
      rowNum:20,        
         pager: '#pageGrid',
         sortname: 'Nombre',
         viewrecords: true,
         sortorder: "desc",               
         jsonReader: {
          root: "rows",
       repeatitems : false,
       page: "page",
       total: "total",
       records: "records",
       id: "0"  //del objeto json, actua como id el primer elemento de rows       
         },       
         editurl: '/AODB2/realTime/arrivalFlight/ArrivalFlightUpdate.action',
         toolbar: [true,"top"],

         ...

Can someone tell me what is wrong? Thank you very much