dolibar PHP customization

I have some customization on dolibar open source PHP. My requirements on payroll module is to make work flow as below Every manager have 3 days to approve his employees salaries or reject with reason as Text field. The 3 days can be change. The system will send notification dialy as reminder to approval for each manager once the payroll uploaded. Once the manager approval the hr manager must approve all salaries then the finance Manager then CEO. On the salaries approval page the status will appear only for the 3main approval (hr manager, finance, CEO) the status to see who approved or reject or pending. Once all approved the system will send the payroll details by email to all employees. Only The account salary manager can upload the salaries using Excel and also do the correction if needed for example if a manager reject one employees salaries. Finally I need 16 additional fields, These fields will used to get the total of salary like below Total=basic salary+fields (1to8)-fields(9to16). Also I need easy way to manualy hide these fields if it not used and rename the label as I need. That's it I hope it's clear The core is Dolibar