OnMouseUp does not work

Hi I wrote a code: void OnMouseUp() { if(Input.GetKey(KeyCode.Mouse2)) rotateByMouse=!rotateByMouse; } I want to switch bool rotateByMouse by middle mouse button-yet this code suprisingly does not work?Anyone knows why?I've checked doc about MonoBehaviour.OnMouseUp(),but there is no mentioning it works only with left mouse button...If so,I have absolutly no idea what's wrong with my code :/