Volume keys in grub2

[Workaround Profi_GMan]

Hello!

As far as I see, the volume keys are mapped to the normal "up" and "down" keys and they function just as up and down keys. So my aim to make them recognized as different keys so I can adjust each of them separately (I want the volume up key to function as the enter key, but I want the normal down key function as down key). 

So how do I do it?

Thank you in advance!