Dialog without close box

Hi!

The dialog displayed by CAPI:CONFIRM-YES-OR-NO has the close box
greyed out.  But if I create my own interfaces and display them with
CAPI:DISPLAY-DIALOG the close box is always active.

I found out that I can get rid of it if I use this create callback for
the interface:

  (lambda (interface)
    (let* ((hwnd (capi:simple-pane-handle interface))
           (menu (win32:get-system-menu hwnd nil)))
      (win32:enable-menu-item menu win32:sc_close win32:mf_grayed)))

Is this OK or will it cause problems?  Is there an easier way to do it
that I'm missing?

Thanks,
Edi.