One of my programs runs on networks - some where the .exe sits on the server and others where the .exe is distributed around the network.

Recently some users (the impatient ones) have managed (by repeated clicking) to load more than one copy of the program onto their work station at the same time. Is there any clever way of stopping this happening without causing problems to those who want to have the .exe just on the server?

Once into the program I can stop two users using one each other's data - that isn't the problem. It is just the loading.

Thanks...