Controlling screen brightness without fn key

Looking for a way to control the screen brightness of a B130 without having to use the built-in keyboard while driving. The computer is riding shotgun in the car. I'm using a keyboard encoder (I-pac) to remotely control my GPS program and media player with custom switches in the center console. It's difficult to reach over and dim the screen with the fn key when it gets dark out using one hand, and I'm certainly not going to attempt it while moving.

Is there another shortcut? I could add more buttons and just hit them in sequence to go up or down as needed. I do something similar now to use Alt+Tab to switch windows, holding the Alt button while tapping Tab.

Or does someone know how to set up a keyboard emulator to send a fn key?

FYI, keyboard encoder info at http://www.ultimarc.com/ipac1.html

Thanks, all.