The application that I wrote was kind of an update for one that we had previously. The guy who did the previous one is as close to a genious as I think I have ever been

He wrote his version in C++, something of which I have no knowledge. But in talking to him about how long my version took because of the whole ping situation, he referenced something called "Threading".

Where my application sends out the broadcast to every user, one at a time, his sent it out to everyone at once.

I didn't really have enough time to look into threading, but you might want to check it out. If it's even possible in VB.

Also, when I was researching ways of doing my app, I came across a few threads about a chat app. Almost designed to be like MSN messenger. That way used app to app broadcasting. I saw a few problems with that, that I didn't really like.
1.) Of course you have to install the application on the clients machine
2.) The application must always be running

This probably wouldn't be that difficult, because you can push out the app any way you like, whether it be logon batch file, script, or an application like SMS or even a self created one like I made
and then you could put it either in the "Run" registry key to run on startup, or the startup folder.

That gets into how technically preficient your users are. would they be like "uhh what is this" and would you have to go into significant explanation of use or could they get along with minimal explanation.

Also you would almost have to write some sort of master application for yourself, and then a minature version for the users.

This is making me almost want to rewrite mine

Ok so anyway, make it so that when a user logs on and there app fires, it sends computer/username to your master app. So you know if they are logged on or not. From this create a list of "User's Online". Then you could also be able to pick one person from the list to send a message to, or send a message to all.

And on their app when they get a message, a window would pop up with the message, and they could reply or disregard, whatever they wanted.

Well, let me know what ya think