Problem updating select box from another windows

Hi I have the following problem:

I followed the screen cast to create complex forms from railscasts so i
create a partial view for my equipments list, the client can add several
different equipments that he select from a select box.

I also made another view (find_equipment) in case looking for the
equipment inside the select box. When i choose a equipment from the view
(find_equipment) I created there is no problem when there is only one
equipment inside
the client form, but when there is more than one equipment and I try to
select it from the select view (find_equipment) it does not update the
select box it should, it update the first select box.

I also have a similar problem when I try to add service details
(_details.html.erb) the thing is that i have configured an observe_field
to watch for voip_product_id like this

      <%= observe_field "voip_product_id",
                        :url => { :controller =>"show_select", :action
=> "get_voip_details"}
the problem is that when I have more than one detail only the first
detail have it select box updated

Can anyone help me please? i'm kind of lost here