Encrypt / Decrypt with Private Tables Question

[Frank1000]

Hi,
while using private tables for the app, I want to encrypt data automatically when entering data to the private table, and decrypt it again, based on user permission, when reading back from the private table.

So far when entering data to the private table, a Google App Script takes care of the encryption OnChange.

Question, how would my Google App Script recieve recognizeable info from AppSheet, when and what is about to be read, so it would hand over decrypted data to the AppSheet app (in case the user is permitted).

Regards,
Frank