Change document history for parts super session (old and new materials)

Hi all,

We have to retrive change history for everyday for parts supersession.

the users will change through PIC01 transaction.

part supersession means users will assign new part number to old part number.. now we have to retrive old and new materials based on the date and time they did.

i have treid with CDHDR and CDPOS..if we give date and time it will come lot of data..

How to resrict the data from these tables.

could you please give the selection cretia for part supper session to CDHDR tables

if any one have idea on part supper session object class and the details please help me

thanks in advance

sriman.