Hi
Suggestion is to check if the user exit is called before the PPMOD feature is called in the Posting program.
If the User exit is called then , you can write code to check if the Cost is center is maintained in IT0027. if Yes then you can overwrite the cost center from WPBP.
I am not sue is the if the user exit get called before going to PPMOD.. that is one that has be checked first.
Not sure if there is any other option to handle this..
Thanks