Hi True Blue.
There're no way to tweaking something with Excel or Windows keyboard. You have 3 option:
1. Using script software:
My source code: http://pastebin.com/7hg3HGm2
In my video, i build to execute file for easy use. If you don't trust this, you can follow instrusion in forums.
2. Mod hardware: You can try this http://atinyhedgehog.za.net/2014/12/cm-storm-devastator-keyboard-mod/.
But you can do it with small switch to turn ON/OFF led backlight, don't need complicated like this mod.
3. Buy a new keyboard.