[cxS]

You can't listen for a key system-wide or "globally" by invoking anything. Invoking has nothing to do with awaiting events. Also the code posted on that SO link, by the OP is terrible. The suggestions are the proper way if you read on. Just should be worth mentioning I thought. SendKeys to invoke the print screen key, is a very stupid/silly and lazy way of doing it.

Ahh, but you can. I've made programs that listen to keys on a global scale, not just when your program is the currently active window.
And if you haven't already noticed, I said I have never tried what I linked. All I did was Google it, just like anybody else can. I don't care what I found. As long as it was on-topic.

lol No... I think you're confused on what "Invoke" means in terms of programming. A lecture on semantics, think of "invoke" as an action, because that's basically what it is in simplest form. This has absolutely nothing to do with listening for anything. So if you say it can be done by invoking keys, what you are essentially saying is that it can be done by executing virtual key events, not listening for them, and which makes no sense.

I never said it was impossible to have global hotkeys, I said it can't be achieved by "invoking" keys. I also read that you hadn't tried anything on that link, but it was irrelevant to what I was pointing out. You don't understand what "invoke" means.