Replace toughness with a derived stat for damage purposes

Hello,
I have created a derived Stat (Mental Toughness) for our Seven Worlds setting. Now I would like my Psionic Powers to do damage vs. the derived Stat (Mental Toughness) rather than the standard toughness value. I have the impression it could be done with the "registerDamageType" functionality in lua. But I can't figure it out. I do have Powers which use the Type "Psionics". Can anybody point me in the right direction.

Thanks a lot
Deryl

IIRC there is the extension for Realms of Cthulhu by Ikael shows how to do this.

Link Here