NET SEND to user with multiple sessions

As part of a software development project I am doing a net send to a username.

However I have encountered a problem where the same user has two NT sessions running. The first session receives the net send message but the second doesn’t. If they exit the first session the second still doesn’t receive the net sends. Apparently this is because of the way that the WINS database works. Ideally I need to determine all of the machines that the user is logged onto and net send to all the machines rather than to a user.

Is there any way of reading the WINS database to get all the machines that a specific user has logged onto?