Adding new damage formulas

[Skurwiel]

Hello! I'd like to get know how to modify the source to add new formulas that can be used in spells' lua scripts. I'm using TFS 0.3.6 and there's this COMBAT_FORMULA_SKILL kind of thing. It calculates the damage depending on what kind of weapon the character is wearing (if he's wearing a club it will use his club fighting skill level when calculating the damage). I want to add formulas for every particular skill (something like COMBAT_FORMULA_SKILL_SWORD) for example.