GUI.Button simulate click

How would I go about simulating a button click to produce the highlighting effect using a key press without actually clicking on the button

I have 9 of these buttons

OnGui

if(GUI.Button(new Rect(Screen.width / 2 - 225 , Screen.height - 56, 50, 50), "1"))
{

}

Update

if (Input.GetKey(KeyCode.Alpha1))
{

}

UPDATE

here is what I did and their might be a better way

    public GUISkin pressed;
 	public GUISkin normal;
	private GUISkin b1;

void Start()	
{
    pressed.button.normal.background = pressed.button.active.background;
    b1 = normal;
}

void Update()
{
    if (Input.GetKey(KeyCode.Alpha1))
    {
		b1 = pressed;
    	StartCoroutine(b1Timer());
 	}
}

IEnumerator b1Timer()
{
	// Waits an amount of time
	yield return new WaitForSeconds(.5f);
	b1 = normal;
}

Edit: changed to answer.

Use the Hover property of a GUI element.