Hi, I'm trying to create a calculated field or a custom function that computes a check digit using the Luhn algorithm. If I input digits in a number field, I would like the calculated field to compute the check digit. Any ideas? I have seen examples for Excel using array formulas or other formulas, but cannot seem to get it to work using FMP. I'm already using a custom function in FMP for the Verhoeff algorithm, but not sure if there is already a similar function for Luhn.