Application.OnKey key codes

The Excel Help file lists a number of codes that can be used to describe keys for use with Application.OnKey, but what are the codes for naming the numeric keypad keys?

I have tried the digits alone but they describe the numbers above the QWERTY row and specifically work only with them; not the numeric keypad. I want to do the opposite.

I have tried enclosing the digits in braces, eg "^{2}" for ctrl-2 but that doesn't do the trick either.

There must surely be codes for them but the Help appears to omit them.

What I really want to do is attach them to macros, because Excel itself only lets you stipulate letters. You can customise Word with pretty well anything on the keyboard. I think we should be able to do the same with Excel.