First of all you have to know that one command should only affect a
change to one AR. This because of your scalability. Second you have to
know a command is always be executed from the command executor.
Possibly you have to redesign your domain so the command should only
affect one AR. The last thing you can do is implement a SAGA. A saga
is ment for keeling track of long running operations. However first
try to redesign you domain. I'm not completely sure how to implement a
saga with ncqrs. Possibly someone else can help you with that one.