Keeping track of changes in sortable elements

Rails
1

Hey all,
I have a sortable element list that looks like this:

    <% @uranks.each do |u| %>
  • <%= u.rank %> <%= u.item.title %>
    • <% end %>

<%= sortable_element ‘yourranking’,
:update => ‘list-info’,
:complete => visual_effect(:highlight, ‘yourranking’),
:url => { :controller=>“lists”,:action => “order”, :listid=>
‘yourranking’} %>

this is the controller code:
def order
params[params[:listid]].each_with_index { |id,idx| Urank.update(id,
:rank => idx) }
end

I would like to keep track of the old ranking before the latest update
like:

Urank.update(id,:rank=>idx,:oldrank=>)

any idea how to do that?

thanx in advance

Pat