Radio button with Observe field

hi, i want a observe field to get which radio button has selected , i was tried , but i was returning both ids when clicked on one among two My View code looks like this: <% fm.food_item.food_options.each do |option| %> <div class="nutrition_food_option"> <input type="radio" id="<%= %>" name="sub_food_taken" value="yes" /> <label for="<%= %>"><%= option.food_item.food_name %></label> </div> <%= observe_field("",     :frequency => 0.5,     :url => { :action => :modify_subfood_intake, :fm =>, :date => date},     :with => "'sub_food_taken='+value") %> <% end %> is it i should call observe field out side loop, then i dont get !!

any ideas thanks