Should not be a problem. As long as your policy has the username, it should apply. Ensure the following:
a) Endpoint agent is installed and registered with your endpoint server
b) You login to the specific endpoint using the username being monitored
c) Your policy has monitor rules for:
- Sender/Recipient = username
AND
- Endpoint Protocol = Copy to Network Share
d) Your Policy is mapped to a Policy group containing your endpoint server.
This shall enable you test the required. Hope this helps?