Bonita BPM Community 7.3.1

Hello, I am a beginner Bonita BPM 7, I did a leave request process, I made two model of business data DemandesConges (StartDate, EndDate, dateRetours, NombreJours, TypeConge, balance, MotifConge) and DossierAdministratif (firstName, lastName, Email...), now I want to know how I can calculate balance of leave in such a way that whenever an employee is applying for leave, the balance of leave subtracts the number of days.
I made a script for the variable of pool but plenty of error

Hello, I am a beginner Bonita BPM 7, I did a leave request process, I made two model of business data DemandesConges (StartDate, EndDate, dateRetours, NombreJours, TypeConge, balance, MotifConge) and DossierAdministratif (firstName, lastName, Email...), now I want to know how I can calculate balance of leave in such a way that whenever an employee is applying for leave, the balance of leave subtracts the number of days.
I made a script for the variable of pool but plenty of error

bonjour , je suis débutant Bonita BPM 7,
j'ai fait un processus de demande de congé , j'ai fait deux modèle de données métier DemandesConges(dateDebut,dateFin,dateRetours,NombreJours,TypeConge,solde,MotifConge)et DossierAdministratif(firstName,lastName,Email..) , maintenant je veut savoir comment je peut calculer solde de congé de tel sorte que chaque fois qu'un employé fait une demande de congé , le solde de congé soustrait le nombre de jours .

j'ai fait un script du variable de pool mais plein d'erreur

I am using Bonita BPM Community Edition Version : 7.3.1 and PostgreSQL have three forms in my process.I want to use data which Bonita by default saves in its configured database. First form is starting process having fields like Title, Start Date, End Date, upload file widget. Second form is changing title, dates and files.Third form is is for only viewing these changes and finalize them. How can i get all these values after third form submission. How can i relate tables and get my variables values.