jQuery Grid Plugin - jqGrid

Hello, I hope, there is a guy who can help me with my “blond” problem:

I want to disable a input field/formedit dependent on a colum - content and have

….
{name:'edatum',    index:'edatum',    width:20,align:'center', sortable:false,editable:true,
editoptions:{size:12},formoptions:{ rowpos:1,colpos:1}, },
{name:'status',    index:'status',    width:20,align:'center', sortable:false,editable:false }
  ],

onSelectRow:  function (form_id){
var id =  jQuery(”#todo”).getGridParam('selrow');  
var ret = jQuery(”#todo”).getRowData(id);
if (ret.status == 'a'  ) 
{ jQuery(”#edatum”,form_id).attr(”disabled”, true);}
,

and in the pager

…

onInitializeForm:function (form_id)
{ jQuery(”#edatum”,form_id).datepicker({showOn: 'button', buttonImage: 'themes/selbst/images/calendar.gif', buttonImageOnly: true, dateFormat:'dd.mm.yy',changeMonth: true, changeYear: true }); }

…

I do not find a solution for hiding or disable or what ever this dammed input-field

Can somebody help me? Greetings

Charlotte