Hi Marcos
The solution proposed by SAP for this scenario is to use a BAPI to post the backflush. Take a look on the following link for more details:
BAPIs for Confirmation in Repetitive Manufacturing - Repetitive Manufacturing (PP-REM) - SAP Library
You would have to develop an interface to read the bar code and call the BAPI. The most common BAPI used for such purpose is BAPI_REPMANCONF1_CREATE_MTS.
BR
Caetano