Not sure why you need a particular key code.
Try the following and see if it may help you out:
1. In your layout, insert new object and choose the keyboard.
2. In your event sheet, "add event" and choose keyboard. Under Keyboard, select "On Key Pressed" -> "Key". When prompted to choose the key you want, just press the "P" on whatever keyboard you are using and C2 will record that key.
3. Go back to the same keyboard event in 2 above and "add another condition" and follow the prompts above. When prompted for a key, press the "Ctrl". At this point you will have two conditions that you want met (Ctrl + P) before your chosen action happens.
4. Then create the action you want to take place.
Caution: Probably most of the world uses the "QWERTY", but there are many other designs as you have found out and it would be difficult to capture all possible corresponding key codes anyway.
One solution is to create you own custom controls on the HUD such as sprite arrows. That way, all and sundry will have to use that set of controls as designed by yourself.