How can I assign a custom function to a system command for my program?

Question

I have an Airline reservation Program and it has lots of menus and sub menus...

Now, I wished to have a system command like Alt+F4 or Ctrl + M to return to the main menu in my program, from wherever the user may be in the program at that time...

So, by pressing Ctrl+M or something like this, I wished to transfer my program to execution of the main menu function again, even when the user is filling details etc. (I save data only in the end).

How can I achieve this ? Please Help!

Answer 1

Also note that I cannot use external headers in this program, so please tell me how to do this using windows.h only...

Thank You for your efforts

Answer 2

Okay, now how do you combine keys?

And, will this execute the menu function from the start everytime I press Ctrl?

if(GetKeyState(VK_LCONTROL))
Menu();

Answer 3

Let me introduce you GetKeyState()
Doc: https://msdn.microsoft.com/es-es/library/windows/desktop/ms646301(v=vs.85).aspx