Dynamic select menu doesn't work for 'form_tag'

Rails
1

Hi everyone,

  I have tried  with the dynamic menu using

"#88 Dynamic Select Menus - RailsCasts " site.
i implemented and it was working fine for ‘form_for’ tag.
But i need to do the same function with ‘form_tag’ as like as,
<% javascript ‘dynamic_states’ %>
<%form_tag do%>

Country: <%= collection_select :id, Country.find(:all), :id, :name, :prompt => "Select a Country" %>

<%end%>

child records doesn’t changed to its corresponding parent when i use
‘form_tag’…
i want to do with ‘form_tag’
Please help me…