create a calc field, JustUpdated, result of type number, defined as OldStatus ≠ NewStatus
Find all closed records, omit;
do a Replace [no dialog ] OldStatus, ActualStatus
do your relookup
Find all the records with JustUpdated = 1
Before the first run do a replace of OldStatus with "Closed" on all the closed orders.
Thanks that saved loads of time, I never realised that the calculation option in replace field contents ran for each record, I thought that it would take the answer from the current record and apply it to all the found records.