Num Pad missing functionality?

[ADROIT]

I love my (old but still kicking) Space Pilot-Pro, Keyboard and Num Pad peripherals. However much of the cad work that I do in CREO requires me to insert underscores in file names i.e. [45326_001_A] I really wish that I could press shift on my keyboard and have the minus key on the numpad turn into an underscore like it does on my regular laptop keyboard when I press shift and the minus key. Is this something I can program into the four option keys at the top of the numpad? Honestly it is my only qualm with the setup and together they have totally changed the way I work