Change button to work OnPress instead of OnClick?

Working with Unity’s UI system, I’m not seeing a way for the buttons to call a method when the button is pressed down. (when the button if first pressed).

It seems the default behavior is to only call the method in the state of OnClick(). Meaning after the button’s been released.

Is their a way to do this?

Thanks.

I want this too. Can we change OnMouseUp to OnMouseDown in default Button ( UI ) ?