Hello Simone,
I assume you have created a new database and that you have now taken the ID from the private members database and referenced this in your ‘Customer ID’ column. If you have done this how are you going to redirect each user to their own document? Also how are you going to ensure that one user cannot view another users file?
This is one of them main reasons why I am also finding this difficult as its hard to find the balance between functionality and users privacy.