Posting Document num not captured in BDC message table

I am working on a dataload program for Asset Transfer using tcode ABUMN. If I run ABUMN online, it will give me the message saying, 'Asset Transaction posted with document no. xxxxxx' after saving the trx. However, I can't capture this message while running the Call Trx/BDX program.

I don't know why the message table is empty after a successful Call Transaction. If there is an error, it will capture it, but no meesage if the trx is successul. I thought the table will capture any message whether it is a 'S' or 'E' or 'W'. It works for other tcodes, but not for tcode ABUMN.

DATA: T_MESSTAB LIKE BDCMSGCOLL OCCURS 0 WITH HEADER LINE.

" Batch Input Message table

call transaction C_TCODE using t_bdcdata

MODE P_MODE

UPDATE P_UPDATE

MESSAGES INTO T_MESSTAB

CAll Transcation is a standard code, so there is need to specify what types of message should be captured.

I remember seeing some threads about the empty message table, and they suggest to use Parameter Id to capture the posting document #. I tried par id ' BLN' and still not able to see anything there.!!

Can anyone help?

Thank you in advance for any help. Greatly appreciated.