Detect Mouse Click in a GUITexture

Hi, currently I managed to put together a simple script that verifies if the player wants to exit the game, and attached it to a GUITexture, but the problem is that wherever I click in the screen, the script starts working. How can I make that it only works when I click the GUITexture?

Verification Code:

public class Verification : MonoBehaviour {

private bool exitClicked = false;

void Update()
{
	if(Input.GetMouseButtonDown(0))
	{
		exitClicked = true;
	}
}
	
void OnGUI () 
{
	if(exitClicked == true)
	{
		GUI.Label(new Rect(Screen.width/2 - 30, Screen.height/2 - 50, 100, 20), "Are You Sure?");
		
		if (GUI.Button (new Rect (Screen.width/2 - 100,Screen.height/2,100,60), "Yes"))
		{
			Application.Quit();
		}
		
		if (GUI.Button (new Rect (Screen.width/2 + 20,Screen.height/2,100,60), "No"))
		{
			exitClicked = false;
		}
	}
}
}

In void Update, you switch exitClicked to true everytime, when user press mouse button 0. It doesn’t depend where pointer is when he press it. You should use OnMouseDown function.