Who was a substitute acting for - at workitem execution

[Susan R. Keohan]

Hello,
 
I have a requirement to find out who a particular user was acting for (as a substitute) when they
execute a specific workitem.  I already know how to see what substitutes are set up, but was hoping
to find something in a workflow log file that would tell me "at the time this workitem was executed,
user B was acting as a substitute for user A".
 
Any help will be greatly appreciated.
--
Susan R. Keohan
SAP Workflow Developer
MIT Lincoln Laboratory
244 Wood Street
LI-200
Lexington, MA. 02420
781-981-3561
skeohan at mit.edu