forms contains collections ... of child-objects

hi all

in my app i have two models (and others of course). article and
article_price and article has many article_prices.
now i would like to create a view for editing all articles and its
current price in a table. when the the price is edited, a new price
with the current params should automatically be add.
the partial wasn't the problem:

      <% for @article in @articles %>
      <% @price = @article.current_price %>
        <tr class="<%= cycle('even', 'odd') %>">
         <td><label for="article_name">
                   <%= text_field( 'article[]', 'name', :size => 0)
         <td><label for="article_unit">
                 <%= text_field 'article[]', 'unit', :size => 5
         <td><label for="article_price_price">
                   <%= text_field_tag
"article_price[#{}][price]", (@price.price if @price), :size
=> 5 %></label></td>
         <td><label for="article_price_unit_quantity">
                  <%= text_field_tag
"article_price[#{}][unit_quantity]", (@price.unit_quantity
if @price), :size => 8 %></label></td>
         <td><label for="article_price_order_number">
                   <%= text_field_tag
"article_price[#{}][order_number]", (@price.order_number if
@price), :size => 8 %></label></td>
      <% end %>

the user can edit every article an its current price in one row.
but the big question ist now, how can i access every article_price of
each article?
the normal solution for collection (update(params[:item].keys,
params[:item].values) doesn't work here because i must integrate the
child-element and have to test if it was edited. the first idea of an
update action looks like this:

#i try to iterate over every price. the id isn't the price id but the
id of the article, so i can identify the right article

params[:article_price].each do
     article = Article.find(price.first) #first because of an array?
     current_price = article.current_price
     if !price[2][:price].empty?
       new_price = => price[2][:price],
                  :unit_quantity => price[2][:unit_quantity],
                  :order_number => price[2][:order_number],
                  :start =>
       article.add_price(new_price) #own method, for adding a price

but thats not working and of course not elegant.
i haven't found any other problems like this, but i guess you know the

thanks a lot.