I've learned to Never say Never, because someone will invariably show you how to do it.

But, I'm pretty sure you can't "sniff" the keystrokes.
A 12megabit/sec half-duplex data stream is beyond the capabilities of a PIC.

Even using a USB "host" like the Vinculum or USBwiz will only work with standard keyboards. The gaming keyboard needs special drivers on the PC that the "host" controller doesn't know about. Which is also why it doesn't work with the KVM's "host controller".

What if you made a separate device with a few push buttons that only sends the KVM commands?
A Little box sitting next to your keyboard.

This should be easy(er) with an 18F2550 or similar.
<br>