Prevent Windows 8 from changing EFI default OS loader

view full story

http://askubuntu.com – I have a Sony VAIO with Windows 8 preinstalled, and I installed Ubuntu 12.10 on a new partition. When the PC boots Grub is display, and I can choose between Windows 8 (didn't worked at the beginning, had to change Grub settings) and Ubuntu. When I select Ubuntu everything is OK, but when I use Windows 8, and I restart Grub isn't displayed anymore (Windows 8 boots immediatly). I booted a USB Pen Drive with Ubuntu, used efibootmgr, and found out that Windows 8 (each time it boots) changes EFI default bootloader from Grub to Windows Loader. How do I change this? I read something about bcdedit, (HowTos)