I'm sorry, Dragon, I'm sure you're a nice guy and all, but you don't seem to have a realistic view of a knife attack. For one thing, if you're grabbing his arm with your opposite arm, then how are you going to punch his jaw? You'd have to punch over the top of your and his arms - not very effective. Secondly, if you even see the knife coming, you'd be best off hitting him pre-emptively rather than waiting for him to attack you first. That's pretty much the law of knife-fighting: be prepared to be cut if you fight, hit first, hit hard, and run when you can. I guess it does depend on how good a martial artist you are, too. Some people would have no problem in a mugging; others would really suffer.