how to simulate a keystroke on a triggerEnter?

I have two rather lengthy and complex scripts in my FPS game that on pressing the F key, I put away my weapon, then pressing it again I draw my weapon. Sounds pretty simple but each script involves toggling several things on and off. I tried rewriting the script using OnTriggerEnter instead of on GetKeyDown but it doesn't work for some reason. o I was wondering if there is a way to simply say something like onTriggerEnter run the script . I found something called inputsimulator.codeplex. but it looks like something that needs to be installed on your computer rather than a script that runs in unity