How to update jQuery dialog after ajax response

Question

I would like to update jQuery dialog after receiving ajax response.

Here is my definition

  var $dialog = jQuery('<div>Wait</div>') .html('Sending your message...<img src="../images/AjaxWait.gif" style="float: left; padding-left: 50px;"/>')
.dialog({      
  modal: true,
  width: 160,
  autoOpen: false,
  resizable: false,
  draggable: false,
});

$dialog.siblings(".ui-dialog-titlebar").hide(); 

and before ajax send:

$dialog.dialog('open').dialog('option', 'height', 50);

And once receiving ajax response I am trying following:

jQuery('.ui-dialog-content').dialog('option', 'buttons', 
                            { "Ok": function() { jQuery(this).dialog('close'); } } );

....but nothing happens...... any idea?