jQuery Grid Plugin - jqGrid

I saw the Dynamically Populate Select Dropdown topic in this forum and my project is working fine when adding a new record in form editing, there's no problem. I'm wondering how can I get the value of first dropdown to pass as parameter(initialid) in the dataUrl of second dropdown box when editing rocords?

 colModel:[

...

{name:'select_one',

editable: true,

edittype:"select",

editoptions: {

dataUrl:'test_one.php',

dataEvents :[

{ type: 'change', fn: function(e) {

var thisval = $(e.target).val();

$.get('test_two.php?myid='+thisval, function(data)

{ var res = $(data).html();

$("#select_two").html(res);

}); // end get

}//end func

} // end type

] // dataevents

} // edit option

},
{name:'select_two',editable: true,edittype:"select", editoptions:{dataUrl:'test_two.php?myid=initialid'}}       

…
],

Thank you in advanced.