Eh? It might help to clarify what you're trying to do, since none of the things you've said really match up!
GRUB isn't a partition manager, it's a boot loader. Partition managers edit / resize / delete / create new partitions of different types across different disks in your system. Boot loaders sit in the MBR and provide a means of selecting what OS you want to boot into on startup. And neither run within the BIOS - that's again, something entirely different.