Rails - Aug 2005 - How to observe radio buttons ?

Hi !

I have a series of radio controls on a form, and I would like to know 
when any of them is selected so I can update another control on the form.

Here is some code:

<%= label ''What style of lights were you thinking of using
?'',
     :estimate, :default_light_style %>

<% @styles.each do |style| -%>
<label><%= radio_button :estimate, :default_light_style, style.last
%>
<%= h style.first %></label>
<% end -%>

<script type="text/javascript">
new Form.Element.EventObserver(''estimate_default_light_style'',
         function(element, value) {alert(''found new value: '' +
value)});
</script>

I never see the alert in my JavaScript.  If I observe the individual 
radio buttons, I do get notified, but only the first time, because the 
value of the radio button never changes afterwards.

Anybody has tips on how I should be handling this ?

Thanks !
François