Hi Joe,
That's the only way I know to determine the number of heliostats in SamUL.
The input boxes that you can edit in the user interface are linked to variables that SAM uses for simulations, and those variables are available in SamUL. SAM does not store the calculated values in the user interface as variables that SamUL can see. That means that you have to write your own script to determine the value of the calculated values as you describe.
Best regards,
Paul.