How to read modifier keys in custom?

[Richie765]

Hey Folks,
I created a custom/brightness to control my brightness using the scroll wheel. Now I want to add a way to control contrast as well. I was hoping to do it with the scroll wheel while SHIFT pressed but I can't find a way to determine if shift is pressed or not. I'd like to avoid creating additional icons because I have 3 screens and I already have 3 icons for the brightness.
Any help or suggestions?