Get the Slider value each frame to update the text content

Builder
1

OS: mac OS Mojave 10.14.2 (18B75)
PsychoPy version (e.g. 1.84.x): Psychopy3.0.2
Standard Standalone? (y/n) : y

Hi,

I want to get the Slider value each frame like rating scale to present a text. I write a code as below. I find the value did not change when i slide the marker on the Slider, and the text did not update. The similar code can works when I use rating scale. So, how to achieve the goal using the Slider.

if slider.getRating() is not None:

    offer_value = slider.getRating()

    print(int(offer_value))

    self = (initial_payoff - int(offer_value))*multiself

    other = int(offer_value)*multiothr

In addition, another problem when I use Slider is the Slider label font size was too big, but I did not find the way to change the font size or height in Builder.