… I have it placed in the « Format » tab, under « Custom Keystroke Script ».
You didn’t place it in « Custom Keystroke Script » but in « Custom Validation Script », so remove it and place this script in « Custom Keystroke Script »:
That should work better.
I guess you indicate comments in the « Notas » field. Where are they located?
If you have a lot of books, I think it would be more userfriendly to enter your data in a cvs file attached to your pdf file!
If you try to do that and need some help, please let me know.