How to change font size in each trial?

I am building SART task and I encountered a problem and it would be great if I get help:
In this task, there should be texts with random font size which I am unable to do. In other words, I do not know how to build the task with random font sizes.

Under font size, put in a variable name (e.g., $fontSize), and set the component to be updated “every repeat”. Create a code component and in the “Begin routine” tab put some code that sets fontSize to a random value.