Math Question for Damage Equation

[Kicks]

So I have a skill that gets stronger when a certain variable increases. But I don't really want the damage to increase that much until it gets to a certain range. Basically like an exponential increase in damage rather than a linear progression.
For referrence I'd like the maximum value of the variable to be about 2500~2800 and the max damage increase to be +200% and the min damage increase to be +0%.
Would it be possible to have this? I basically just need the equation and how i could put it into rgss.

 

[Sheol]

You mean a random value ?

var = 2500 + rand(300)

 

[vgvgf]

Something like this?:

damage = skilldamage +  [variable ** 2 / variable ** 1.5, skilldamage * 3].max

For putting the extra damage script: ( The added script is in red)

class Game_Battler
  def skill_effect(user, skill)
    self.critical = false
    if ((skill.scope == 3 or skill.scope == 4) and self.hp == 0) or
       ((skill.scope == 5 or skill.scope == 6) and self.hp >= 1)
      return false
    end
    effective = false
    effective |= skill.common_event_id > 0
    hit = skill.hit
    if skill.atk_f > 0
      hit *= user.hit / 100
    end
    hit_result = (rand(100) < hit)
    effective |= hit < 100
    if hit_result == true
      power = skill.power + user.atk * skill.atk_f / 100
      if power > 0
        power -= self.pdef * skill.pdef_f / 200
        power -= self.mdef * skill.mdef_f / 200
        power = [power, 0].max
      end
      rate = 20
      rate += (user.str * skill.str_f / 100)
      rate += (user.dex * skill.dex_f / 100)
      rate += (user.agi * skill.agi_f / 100)
      rate += (user.int * skill.int_f / 100)
      self.damage = power * rate / 20
      self.damage *= elements_correct(skill.element_set)
      self.damage /= 100
      if self.damage > 0
         if self.guarding?
          self.damage /= 2
        end
      end
      if self.damage.abs > 0
        amp = [self.damage.abs * skill.variance / 100, 1].max
        self.damage += rand(amp+1) + rand(amp+1) - amp
      end
      eva = 8 * self.agi / user.dex + self.eva
      [COLOR=Red]self.damage +=  [variable ** 2 / variable ** 1.5, self.damage * 3].max[/COLOR]
      hit = self.damage < 0 ? 100 : 100 - eva * skill.eva_f / 100
      hit = self.cant_evade? ? 100 : hit
      hit_result = (rand(100) < hit)
      effective |= hit < 100
    end
    if hit_result == true
      if skill.power != 0 and skill.atk_f > 0
        remove_states_shock
        effective = true
      end
      last_hp = self.hp
      self.hp -= self.damage
      effective |= self.hp != last_hp
      @state_changed = false
      effective |= states_plus(skill.plus_state_set)
      effective |= states_minus(skill.minus_state_set)
      if skill.power == 0
        self.damage = ""
        unless @state_changed
          self.damage = "Miss"
        end
      end
    else
      self.damage = "Miss"
    end
    unless $game_temp.in_battle
      self.damage = nil
    end
    return effective
  end
end