larryd:
After reading this, my eyes hurt
Mine didn't 
Why not ask your question using basic english and describe things in basic electronic terms.
I actually understand quite well what he wants.
the employees will be inside a vehicle
Does the button need to be inside the vehicle?
How far is the button from the PC?
I assume the target PC is running windows?
You can send serial data from the arduino to the pc.
Use powershell to act on the incoming serial data.
See these links:
https://learn.sparkfun.com/tutorials/terminal-basics/command-line-windows-mac-linux
or run processing with the exec command
maybe also worth looking:
EDIT:
I overlooked that the sparkfun pro micro can actually act as keyboard, as mentioned above.
https://www.sparkfun.com/tutorials/337
This is might be an easier solution, depending on distance / wireless requirements.