GetAsyncKeyState
This function determines whether a key is up or down at the time the function is called, and whether the key was pressed after a previous call to GetAsyncKeyState.

SHORT GetAsyncKeyState(
int vKey );
Parameters
vKey
[in] Specifies one of 256 possible virtual-key codes. For more information, see Virtual-Key Codes.
You can use left- and right-distinguishing constants to specify certain keys. For more information about constants, see Remarks.

Return Values
If the function succeeds, the return value specifies whether the key was pressed since the last call to GetAsyncKeyState, and whether the key is currently up or down. If the most significant bit is set, the key is down. The least significant bit is not valid in Windows CE, and should be ignored. GetAsyncKeyState returns the current key state even if a window in another thread or process currently has the keyboard focus.