If your EHLLAPI application program is sending a series of transactions
to the host, you might need to prevent the user from gaining access
to that session until your application processing is complete.
The keyboard input that a user makes while the keyboard is locked
by this function is enqueued and processed after the session is terminated.
This function locks both the mouse and the keyboard input. The
application program must unlock the presentation space to enable either
the mouse or the keyboard input.