unity – How do i making my button UI can hold?

So i want to make my button can hold or do stuff when hold, in this case I want to make grab function, when the button down can grab but if button up its not grab.

before that I already have the function and using Standart Asset with crossplatform.

here the preview

that’s the current button

and here the script :

void Update()
    {

        Physics2D.queriesStartInColliders = false;
        RaycastHit2D hit = Physics2D.Raycast(transform.position, Vector2.right * transform.localScale.x, distance, boxMask);

        if (PushKey())
        {
            isGrab = !isGrab;

            if (hit.collider != null && hit.collider.gameObject.tag == "Box" && isGrab)
            {
                box = hit.collider.gameObject;
                box.GetComponent<FixedJoint2D>().connectedBody = this.GetComponent<Rigidbody2D>();
                box.GetComponent<FixedJoint2D>().enabled = true;
                box.GetComponent<Rigidbody2D>().gravityScale = 1;
                box.GetComponent<Rigidbody2D>().mass = 1;

            }
            else if (!isGrab)
            {
                box.GetComponent<FixedJoint2D>().enabled = false;
                box.GetComponent<Rigidbody2D>().gravityScale = 6;
                box.GetComponent<Rigidbody2D>().mass = 6;
            }
        }
    }

    public bool PushKey()
    {
        return CrossPlatformInputManager.GetButtonDown("E");
    }

the current function mean first tap button grab activated and second tap button grab deactivated.