I am not sure about it working across a home network. I only know that it does work to the local pc (from a BAT file).
To be sure, you should check the path is correct (instead of taking mine for gospel) in case your installation gives the path a different name.
Click START and type in msg.exe. It should appear at the top of the search results. Then right-click on it, chose properties and it will show you the extended path to where that program is currently residing. THAT is the path you need to insert into your
BAT file.
I will reiterate, Im not sure it will recognise usernames across a network though. (For your information, I use it in a BAT file designed to load a program on various conditions being met, and the message is issued to the local user, ie ME, to inform me if
those conditions are not met).