issue related CDHDR and CDPOS

Hello.

I have three 'z' fields used in LIKP for updating POD(proof of delivery)information.

the three fields are : zz_podat, zz_uname, zz_datum

this fields are updated to DB(LIKP table) using Modify command.

But when modify command is used, the revelant changes are not updated to standard tables CDHDR(change document header), CDPOS(change doucment item).

May i know, how to get information of change doucment histroy of a field. When modify command is used.