Swap Values via Model in an onChange Event Within submit_tag Helper?

I’m new to RoR and (and programming) and am having trouble wrapping my
head around how to get this working. What I’m trying to do is autofill
a web form with values I select from a drop-down menu. I want to pull
these values in from my Openers table.

My DB Model is called Openers and has the following fields:

id
description
subject
body

My Controller is called bar_controller.rb and contains only 1 method
which pulls all the records from Openers and orders them by
description:

class BarController < ApplicationController

def bar
@show_openers = Opener.find(:all, :order => “description”)
end

end

I have 3 Views located user app/views/bar that make up a 2 column
framed page. The first file is called index.html.erb and sets up the
frames:

The second file is called bar.html.erb and fills in the upper portion
(top 10% of the page).

<%= javascript_include_tag :defaults %>

<% form_for :bar, :url => { :action => :bar } do |form| %>
<%= collection_select(“openers”, “opener_id”,
@show_openers, :id, :description ) %>
<%= submit_tag “insert opener”,
:onClick =>
“parent.formtofill.document.form1.messagesubject.value=‘HERE_IS_SUBJECT’,
parent.formtofill.document.form1.messagebody.value=‘HERE_IS_BODY’” %>
<% end %>

The last file is called formtofill.html.erb and fills in the bottom
90% of the page. It contains the form that I want to auto-populate
with the values defined in bar.html.erb.

Subject:

Body:

Right now I’ve got the descriptions populating the dropdown and the
onClick will stuff the static HERE_IS_SUBJECT and HERE_IS_BODY into
the correct form fields, but there are still a few things I’m having
trouble with:

  1. How do I access the subject and body info?
  2. Once question 1 is solved, how do I update the HERE_IS_SUBJECT and
    HERE_IS_BODY values on an onChange event (within the submit_tag
    helper) with the matching Openers.subject and Openers.body values for
    the Openers.description selection?

Thanks in advance for any help!!!