Searches for the next (or previous) window in the window manager's list.
Specifies whether the function returns a pointer to the next window or the previous window. It can be either GW_HWNDNEXT, which returns the window that follows the CWnd object on the window manager's list, or GW_HWNDPREV, which returns the previous window on the window manager's list.
The window manager's list contains entries for all top-level windows, their associated child windows, and the child windows of any child windows.
If CWnd is a top-level window, the function searches for the next (or previous) top-level window; if CWnd is a child window, the function searches for the next (or previous) child window.