How to Check If an Object Is with certain part of the Screen

Hello I’m trying to check if an Object is with in Part of a screen then a InSpace = true, if it is not in that part of the screen then the InSpace = false.

I have attempted at it, but it only works with in screen space and it does not work in a specific part of the camera’s screen space.

What do I have to do to make this work?

    public Transform target;
    public Camera camera;
    bool InSpace = false;
    private void OnGUI()
    {
        Vector3 screenPoint = camera.WorldToViewportPoint(target.position);
        bool onScreen = screenPoint.z > 0 && screenPoint.x > 0 && screenPoint.x < 1 && screenPoint.y > 0 && screenPoint.y < 1;
        if (onScreen)
        {
            InSpace = true;
        }
        else
        {
            InSpace = false;
            Debug.Log("Object is Off Screen");
        }

    }

Just add colliders and check isTrigger. Add two functions onTriggerEnter() and onTriggerExit() and relay your boolean based on that.