Getting mean accuracy at the end of practice block

OS (Win11):
PsychoPy version (2024.1.3):
What are you trying to achieve?:
I have a cued switching task. I am trying to get the mean accuracy of the practice block to get a hint whether the participants got hold of the experiment or not. At the end of the practice block, a screen should appear displaying their mean accuracy in percentage form.
Please help me achieve this in psychopy builder.