Hi Patrick - Thanks for getting back to me. Unfortunately, I'm a little confused. The field I am trying make read-only is called Migration_Date. The name of my repeating section is called 'MyRepeatingGroup'. Per your suggestion, I have created a hidden field called Count_Migration_Date. I set its default value to Count(Migration_Date). Is this correct? As for the rule, should it be a 'Conditional Formatting' rule on the Migration_Date field where I compare Count_Migration_Date to Count(MyRepeatingGroup), and if they are unequal, check the 'Read-Only' checkbox?
I don't think this is correct because it is not working. Any more guidance you can provide would be greatly appreciated!