Dirty Fields in Rails 1.2.6

Hi Friends,

I am using Rails 1.2.6 in my application. I need to use the
functionality of "dirty fields" (getting previous value of an object's
attributes). I know "Dirty fields" features are already in edge rails.
But i want to do the same in my current rails version... any ideas?

i tried the dirty plugin which is given here
(http://dev.rubyonrails.org/browser/trunk/activerecord/lib/active_record/dirty.rb?rev=9127)

After including this module (from the above url) to my active record
base class, my active record object are able to show the status -
whether object is changed or not (using the method - obj.changed? ) but
they are unable to show the changed values, instead it always give an
empty hash ( method - "obj.changes")

I need to get the previous value for the modified object's attributes

can anybody help on this?