Enable Camera Image Effect on Button Down

Hi there, i'm new to Unity 3D and i have a small question to ask. I'm currently working on a 3rd Person Adventure and so far everything is going great. I'm not experienced in Javascript so please bear with me.

The code i'm requesting is that when i hit the any of the Vertical (Up/Down arrow) keys (in which the player moves forward), the image effect, Fisheye, attached to the camera enables while the player is holding the up/down arrow key. Once the player let's go of the arrow keys, the image effect is disabled. May i please have the code to this? Thank you :)

FisheyeController.js

private var effect : Fisheye;
effect = GetComponent("Fisheye");

function Update () 
{
    var keysWS = Input.GetKey(KeyCode.W) || Input.GetKey(KeyCode.S);
    effect.enabled = keysWS;
}


However I think you want to apply a smooth transition on the bend instead.

SmoothFisheyeController.js

private var effect : Fisheye;
effect = GetComponent("Fisheye");

var strengthX : float = 0.05f;
var strengthY : float = 0.05f;
var speed : float = 0.05f;

function Update () 
{
    var keysWS = Input.GetKey(KeyCode.W) || Input.GetKey(KeyCode.S);
    var targetX = keysWS ? strengthX : 0;
    var targetY = keysWS ? strengthY : 0;
    var move = Time.deltaTime * speed;
    effect.strengthX = Mathf.MoveTowards(effect.strengthX, targetX, move);
    effect.strengthY = Mathf.MoveTowards(effect.strengthY, targetY, move);
}