POP up Message on client application

i am trying to make an application (admin + client) which can pop up messages on the network computer in which client application is installed.

means first i will install client application on my network computers and when i will send a message from admin pannel, all client application should pop up
that message on the window screen, which is sent by the admin.

so that it can be used to broadcast the message to all nodes, and the client application not need to be signned in, it should auto start with windows

need help it in making in .net or vb6:sick::confused: