function gunProjectile::onDamage(%this,%obj,%col,%pos,%fade,%normal)
{
//Ondamage has the "in minigame" checks, so will only be called if the player can be "Damaged" (Healed) by it
%col.setDamageLevel(%col.getDamageLevel()-50);
Parent::onDamage(%this,%obj,%col,%pos,%fade,%normal);
}
Change the 50 to however much you want it to heal.