GetKey decreasing the value per frame by time.delta

I want to make an GetKey on mouse1 it be decrease the "timeofvalue" to 0 by time.delta or fixed delta it doesnt matter pls help if (Input.GetKey(KeyCode.Mouse1) && timedown == true) { timeofvalue += 0.01f * Time.fixedDeltaTime; vignette.intensity.value = timeofvalue; } if (Input.GetKeyUp(KeyCode.Mouse1)) { timeofvalue = 0.30f; vignette.intensity.value = timeofvalue; }