It is possible to add support for NumPad keys in a CUI.
For instance, you can assign an OSnap override to each of the numbers on the number pad, and use the number pad during the middle of a command to supply the override, as long as NumLock is off.
The attached file has OSnap overrides for each of the numbers 0-9.
0 = EndP
1 = Mid
2 = Cen
3 = Nod
4 = Qua
5 = Int
6 = Ins
7 = Per
8 = Tan
9 = Nea
F1 has also been redefined to be the <Escape> key instead of displaying Help.