software generated customer specific field

Hi,
I am trying to generate a random 128-bit uuid for each DUT and burn to the OTP header using the software generated customer specific field for the GUI and then log to a file.

I read in the user manual that I should change the gplt_sw_customer_field function, I activated info printouts to verify that the function was actually called but it didn't appear. When is the function actually supposed to be called? I have enabled the checkbox.