jqgrid change cell value and stay in edit mode
editoptions: {
    dataEvents: [
        {
            type: 'blur',
            fn: function(e) {
                var newCodeValue = $(e.target).val();
                // get the information from any source about the
                // description of based on the new code value
                // and construct full new HTML contain of the "description"
                // cell. It should include "<input>", "<select>" or
                // some another input elements. Let us you save the result
                // in the variable descriptionEditHtml then you can use

                // populate descriptionEditHtml in the "description" edit cell
                if ($(e.target).is('.FormElement')) {
                    // form editing
                    var form = $(e.target).closest('form.FormGrid');
                    $("#description.FormElement",form[0]).html(descriptionEditHtml);
                } else {
                    // inline editing
                    var row = $(e.target).closest('tr.jqgrow');
                    var rowId = row.attr('id');
                    $("#"+rowId+"_description",row[0]).html(descriptionEditHtml);
                }
            }
        }
    ]
}

editrules = new
{
custom = true,
custom_func = function( val, col ) { ... }
 },