Editing built in classes?

Hi

I have been playing around with the tweening class, and wanted to make some tweeks to the motion inside the Back class, but when I tried added in some trace code it was like the /classes/functions were not being called?

I went as far as renaming the easing folder to see what would happed, but nothing did, swf continued to play fine as if nothing had happened…

can anyone tell me where im going wrong the files I was looking at were in
C:\Program Files\Macromedia\Flash MX 2004\en\First Run\Classes\mx ransitions

are the classes it uses at run time in a different place?