Try this:
local combat = createCombatObject()
setCombatParam(combat, COMBAT_PARAM_BLOCKARMOR, 1)
setCombatParam(combat, COMBAT_PARAM_BLOCKSHIELD, 1)
setCombatParam(combat, COMBAT_PARAM_TYPE, COMBAT_PHYSICALDAMAGE)
setCombatFormula(combat, COMBAT_FORMULA_SKILL, 0, 0, 1.0, 0)
function...