Hi Jack,
Not sure I'm understanding your question correctly, but maybe this helps: on the DRAW object there is a method GetDetail2 (or GetDetail if you are on an older system) which has import parameter GetStatusLog. Call this method with GetStatusLog = X and the returned table STATUSLOG has which user set which status.
You could wrap the BAPI in your own method to return just the user who set the status that is relevant to this workflow instance.
I hope this is helpful!
Margaret