How much data is written to the database by one specific module?

Hi,

   My customer wants to know how much data is written to the database by one particular module during a given time period. The module may be run by a number of database sessions, perhaps more than one running concurrently, but the sessions can be identified by the contents of the 'module' column in v$session. I have investigated using the contents of 'delta_write_io_bytes' from dba_hist_active_sess_history, but these figures seem far too high (I guess they include data written to undo, redo, etc.). We may have to resort to database auditing, but I wonder whether the information required is already accessible