All the errors are entered into an internal table of type 
BDCMSGCOLL.Then we can loop over the message table to write 
out any messages that were entered into it.

We will catch errors in the call transcation explicitly by 
using Structure BDCMSGCOLL.
and FUNCITNO MODULE 'WRITE_FORMAT'.

Ex:
Data  :  bdc_msg type table of bdcmsgcoll with header line,
   bdc_tab type table of bdcdata with header line.

CALL TRANSACTION  'MM01' using Bdc_tab mode N
                                      updte S
                         messages into bdc_msg.
if sy-subrc = 0.
   perform  Error.
  clear bdc_msg.
  refresh bdc_msg.
endif.
 Read table bdc_msg with key msgtype = 'E'.

 if sy-subrc = 0.
 call function 'FORMAT_MESSAGE'.
...
..
..

SORRY IT IS NOT WRITE_FORMAT ....
IT IS FORMAT_MESSAGE. I WAS MISTYPED IT PLEASE IGNORE IT.