change history question

Hi all,

I am doing the change history function in CMS module. I have some questions for it.

The requirement is there is a Z table needs to do screen enhancement by using BDT and has change history function as well.

I have done the following steps:

1, Create the Z table and tick 'change document' in data element of all fields to.

2, Create the change document object in SCDO and build up the related function group and get FM 'XXX_write_document'(XXX is table name).

3, Assign table (screen) fields to table database fields.

4, In BDT event, I call FM 'BUS_COBJECTID_COLLECT', I just gave it the name of the change document object and the key field value of the table.

But it didn't work. Actually, FM 'XXX_write_document' is not triggered when I debug the program so that no data entries in CDHDR.

Any step missing?