Open flash chart and ajax

Hi
I want to refresh a graph For that what should I do.The following is
an example from the site
My controller code like

def dashboard
@graph =
open_flash_chart_object(600,300,"#{request_summary_graph_path}", true)
end

def draw_summary_graph
g = Graph.new
g.title( ‘Users vs. Ram - 24h statistics’, ‘{color: #7E97A6;
font-size: 20; }’ )
g.set_data([289,198,143,126,98,96,124,164,213,238,256,263,265,294,291,289])
etc etc…
render :text => g.render

end

and my view (dashboard.html.erb ) like

<%= link_to_remote 'Refresh', {:url => request_summary_graph_path}, :update => "test_div_this" %>
<%= @graph %>
     What i am trying to do when clicking on Refresh link the

portion inside div “test_div”
refreshed But this does not happen Please help

Thanks in advance
Sijo