Change history issue for custom table

Hi All,

I have created a new assignment block using Rapid application storing the data into custom table  which is added in BP page(BP_HEAD).

Now I need to track the changes of the  custom table in change history. I have created a new change document  for custom table using the tcode SCDO.

it is created a new function module *WRITE_DOCUMENT.

1. Still CDHDR and CDPOS tables are not updating the changes data when I am doing the modifications in assignment block.

2. Do i need to call FM   "WRITE_DOCUMENT to update the CDHDR and CDPOS tables?

I found one  doc https://scn.sap.com/thread/3383141,  this link is going to help me once the CDHDR and CDPOS tables.

regards,rama