I want OnClick to fire the same frame that the button is clicked

I made a pause button that then pauses the game by setting Time.timescale = 0. I use the editors On Click {} event. The code looks like this:

public class PauseAndPlay : MonoBehaviour
{
public GameObject pauseButton;
public GameObject playButton;

public void Pause()
{
	
	SaveAndLoad.saveAndLoad.Pause();
	pauseButton.SetActive(false);
	playButton.SetActive(true);

}

public void Play()
{
	pauseButton.SetActive(true);
	playButton.SetActive(false);
	SaveAndLoad.saveAndLoad.Unpause();
}

}

The problem then comes when my player continues to move for a bit even though the game has been paused with Time.timescale.
I move my player like so:

//If mousepress is detected
if (Input.GetMouseButton(0))
{

		//set the place as a vector
		targetPos = cam.ScreenToWorldPoint(Input.mousePosition);
		targetPos.z = 0;
		//Get screen height and width
		screenBounds = cam.ScreenToWorldPoint(new Vector3 (Screen.width, Screen.height, 0));
		//Clamp the target position so that player can't leave camera view
		targetPos.y = Mathf.Clamp(targetPos.y, (screenBounds.z - renderSizeY), (screenBounds.y-renderSizeY));
		targetPos.x = Mathf.Clamp(targetPos.x, (screenBounds.z - renderSizeX), (screenBounds.x - renderSizeX -2/*-2 because of next line where + Vector3.right * 2 */));
		//move to the place, but a bit forward so the finger doesn't obscure the sprite. ActualSpeed() is an int * Time.deltaTime
		transform.position = Vector3.MoveTowards(transform.position,targetPos + Vector3.right * 2, ActualSpeed());
	}

This happens in the Update loop.
So I suspect, after a few tests, that the OnClick event doesn’t happen until you stop clicking, essentially GetMouseButtonUp(0) sort of thing. With the way movement is implemented in my game I would need to pause it on the GetMouseButtonDown(0) instead.
Anyone know how this can be achieved?

Found the answer myself. In case someone else needs it:
Use OnPointerDown

Just do it the same way as in the link, even making it public. OnPointerDown will fire when the object is clicked.