controller.rb

def index
  if params[:client_id].present? && params[:listing_group_id].present?
    @deltas = some lookup...
    respond_with @deltas, ajax: { partial: render_to_string(partial: 'histories', locals: {deltas: @deltas}) }
  else
    data_table_request(catalog_item_deltas_table) # or whatever
  end
end

example.html.haml

= @catalog_items_table

%div{style: 'display: none'}
  #deltas

:javascript
  function loadHistories(client_id, listing_group_id){
  $.ajax({
    type: 'GET',
    url: '/client/'+client_id+'/listing_group/'+listing_group_id+'/catalog_item_deltas.ajax',
    success: function(data){
      $('#deltas').html(data.partial);
      $.fancybox($('#deltas'));
    },  
    error: function(errors){
      alert("Got error");
    }   
  })  
  }