Redmine

Greetings folks!

I need to integrate the time log of Redmine with an oracle application and is my first time with redmine/ruby/rails so take it easy.

Redmine version                3.3.1.stable
Ruby version                   2.3.1-p112 (2016-04-26) [x86_64-linux]
Rails version                  4.2.7.1
Environment                    production
Database adapter               Mysql2
MySQL 5.7.17

Basically when a user confirm a time log, these information must be send to an oracle database. Besides that i need to include additional fields like that:

Initially i tried to make a plugin using ControllerTimelogEditBeforeSave hook, here i call a procedure from oracle to insert, update or remove the correspondent register. It works, but unfortunately if a exception return from procedure, i can't show that error to user and can't abort the timelog insert.

The point is, how can i do this integration, how i stop the timelog insert, show the error message to user, and how can i create a new field in time entry by plugin and not via custom fields?

Sorry for my bad English.