OK, so I guess I can add a neogrub entry to the Windows boot manager, then make it call neogrub directly instead of displaying a first menu, then neogrub issues a beep and display its own menu, where I can select Windows 7 or 10. Is it all correct?
Regarding the procedure to make neogrub beep, I recall having read somewhere that one must put a hexadecimal character on a given line of the menu.lst file, but don't recall exactly how to do it. Can you explain please?