It is possible that you might be able to do it in hardware.
http://www.computer-engineering.org/ has some assembly code that allows PICs to emulate PS/2 keyboards, as well as descriptions of the protocols and the functions of the 8048 and 8042. With that, and some skill, toil, and luck, you could probably hack together a quite clever system allowing you to clone one keyboard onto an arbitrary number of systems.
If you don't fancy trying that(can't say that I blame you), you might be lucky enough to have it work with something simpler. It could be as easy as building an adapter that connects the keyboard to both systems(though I'd cut the +5 in one of the connections, and tie the systems' grounds together). As keyboards speak a bidirectional serial protocol, they might be horribly, horribly confused by this, so it might not work at all. It could also be that, for impedance reasons or similar, it doesn't work, in which case something of intermediate complexity, involving optocouplers or similar, might help.
I'm sorry to report that I could find no off the shelf hardware device for this purpose. On the software side, I've never heard of such a thing for Windows(which I would guess you are using, if you are a VB fellow. If you are using a *NIX, though, it should be reasonably(for some value of reasonably) simple. You would need to set up an app on one machine that takes the output of the keyboard device and writes it to the keyboard devices of all the other machines, over the network. This could be an obnoxious bit of scripting and permissions twiddling, depending on the details; but the device structure of *NIX should make it quite simple in principle. That probably doesn't help you, though. Good luck.
