Knife on clicked rather than "F" key. Any help?

Well, some of you might recognize this script. Its by Turbo Fusion. Im editing it so instead of a gun its a knife. So far its really cool, but however it requires you to press f to knife and I cannot figure out how to make it on click. Ive tried a lot of things and this is my last resort :p

The turbo fusion script in my inventory because it is too big to be on here. Titled 'TURBOSCRITPINGHELPERS'

http://www.roblox.com/TURBOSCRITPINGHELPERS-item?id=293672709

Try putting the assets into a tool or hopperbin and make a .activated script

You have to either find out if the knife is scripted to use F key and change it to left mouse click or just script it saying 'f' key = false (for using), mousebuttondownleft = true (something like that)

hope it helps!