hot to send a key message to another program?

I am attempting to create a bot for a fps game that can make another program think i am holding down the shift button(because thats the button you hold down when you want your character to run) when i press a key (for example F5) once and stop when i press it again.

this is a small part of a program.
So how would i go about writing that? if someone could just get me started i could probobly take it from there.

You'll probably want to use the keybd_event function.

but how to i make it keep sending the shift down message to the game? , that was my main problem

Send the message that the shift key has been pressed down, but never send a message that the shift key has been released.

(or continually send the shift key is down message if that doesn't work)

SendMessage(hwnd, WM_KEYDOWN, VK_SHIFT, NULL);
would that work?

and what is the #include statment for VK? is it <winuser.h>?