How to make 2 keys activate something when pressed at the same time?

Im trying to make a control panel which will open when you press CTRL ad ALT. I have tried if "key == 29 and 56 then" thinking it would work. Any ideas?

I don't think this is possible to do, because you can't tell when someone stops holding a key down.

The best way to do this would be to start a very short timer (say, a tenth of a second or so) when either key is pressed. If the other key is pressed before the timer expires, you could consider them to have been pressed at the same time.