Hi kflores01,
I haven't actually tried this, but from the LPL it appears that you don't use Workunit at all, and you have these options: - pass in nothing, which moves any WU which is complete or cancelled to history - or pass in begin and end date, which moves any WU which is complete or cancelled and the PfiWorkunit.CloseDate is between begin and end - or pass in a ServiceName OR a Flow Name, which moves any WU which is complete or cancelled and which has that Service or Flow Name and has any date - or pass in both Begin and End Date and a Service or Flow Name to combine the two options.
Attached is the LPL for that action.