How to prevent Update Manager from installing grub?

[Piscium]

I was having problems with Grub2 on Karmic, so uninstalled it, got the sources from the Grub website, built it, and it works well.

Unfortunately the kernel update (2.6.31-15) caused grub-pc and grub-common to be reinstalled, so I had to manually uninstall them.

Is there a way to prevent Update Manager from installing grub-pc and grub-common the next time there is a new kernel available? Some APT command?

Thanks in advance.