I'm thinking that you are looking at Disarm, Trip or Stun.
The wording for Disarm is:
Disarm opponent (Attack and Defence) – The opponent must roll an opposed test of his
Combat Skill vs. the original attack roll (if the attacker won) or the original parry roll (if the
defender won). If the recipient of the disarm fails, he loses his weapon. Two handed or entangling
weapon wielders may add a bonus of +20% to their skill for this check. Disarming works only
on creatures of up to twice the attacker’s STR. If the attacker has a hand free, he can grab the
opponent’s weapon on a successful Disarm.
So Opposed test of Combat skill vs. Original Attack or Parry roll.
for Stun;
Stun Location (Bludgeon Weapons, Attacker Only)– Weapons such as maces, hammers and
so on, can temporarily numb the location struck. The defender must roll an opposed test of
his Resilience vs. the original attack roll. If the defender fails, then a limb is rendered useless, a
torso blow causes the foe to stagger winded (may only defend), or a head shot renders the foe
unconscious. The duration of incapacitation is equal, in Combat Actions, to the damage that
penetrated the armour. If no damage penetrated, then the impact was insufficient to stun.
So Opposed roll of Resilience vs. Original Attack roll.
and for Trip;
Trip opponent (Attack and Defence) – The opponent must roll an Opposed Test of Evade vs.
the original attack roll (if the attacker won) or the original parry roll (if the defender won). If
the opponent fails, he falls prone. Quadruped opponents may substitute their Athletics skill for
Evade and gain a +20% bonus to their skill for this test.
So Opposed test of Evade vs. original Attack or Parry roll.
Opposed tests p44/45
The winner of the test is the
one who gains the higher level of success; if both participants have the same level of success,
then the winner is the one with the higher dice roll within his skill range. (In the extremely
unlikely situation that both Adventurers have exactly the same dice result and the same Level
of Success, then the Adventurer with the highest skill wins. If it is still a draw, toss a coin to
determine the winner!)
So if both have a Success then the player with the higher roll still under his skill is the winner.
E.g. Alaric has 67% is his Sword and Shield skill.
BBEG has 87% in his fighting skill.
If both roll under their respective skills then the one who has the higher value in the winner.
So if BBEG rolls a 53%, a success and Alaric rolls a 69%, a failure. The BBEG chooses Disarm so
Alaric must roll his Sword and shield skill and score more than 53% but less than 67% or be disarmed.
Substitute Resilience or Evade for Stun or Trip.