badi or exit for cj20n --- PS module

Hi All,

I need to activate change log in t-code cj20n like in va02.

(for seeing the change log of va02 follow the procerdure,

go to va02

then enter any sales order

press enter

when the sales order is displayed

then click on Environment - Changes

when the screen appears,

click on execute

now the screen is displayed

if we want to see the changes then

select one of them

and double click).

But i don't know the Exit or BADI for that.

so please suggest me the exit or badi name.