Take Screen Shot onGUI

Hello Everyone! I have attached the following code below to my camera and am able to take a screenshot by hitting the letter K. But how would I rework it to take a screenshot when the player clicks on a GUI button? Thank you for your input!
K.

var resWidth : int = 4096; var resHeight : int = 2232;

function Update() { if (Input.GetKeyDown ("k")) { var rt = new RenderTexture(resWidth, resHeight, 24);
camera.targetTexture = rt; var screenShot = new Texture2D(resWidth, resHeight, TextureFormat.RGB24, false); camera.Render(); RenderTexture.active = rt; screenShot.ReadPixels(Rect(0, 0, resWidth, resHeight), 0, 0); RenderTexture.active = null; // JC: added to avoid errors camera.targetTexture = null; Destroy(rt); var bytes = screenShot.EncodeToPNG(); System.IO.File.WriteAllBytes(Application.dataPath + "/screenshots/screen" + System.DateTime.Now.ToString("dd-MM-yyyy_HH-mm-ss") + ".png", bytes); }
}