HWND pascal GetNextWindow(HWND hWnd, WORD wFlag)
 <MS-WINDOWS equivalent>

  This function traverses the window tree in search for the next or
previous window relative to the window passed as the first argument.
If the passed window is a top-level window (ie - a window with no
parent), then this function will retrieve the next or previous
top-level window. If the passed window is a child window, then this
function will retrieve the next or previous sibling of that child
window.

Parameters
  hWnd is the handle of the window to query.
  wFlag can be one of the following :
    GW_HWNDNEXT - retrieves the next window on the window list
    GW_HWNDPREV - retrieves the previous window onthe window list

Returns
  The handle of the retrieved window, or NULLWND if no window was
retrieved, or if there was no previous or next sibling. Please note
that this function does not wrap around in its searches.