To create a window that has vertical and horizontal scroll bars, modify the call to the CreateWindow function so that it looks like this:
hWnd = CreateWindow("InputWClass",
"Input Sample Window",
WS_OVERLAPPEDWINDOW | WS_HSCROLL | WS_VSCROLL,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
hinst,
NULL);