Project in non profit organization and payroll

I want to apply this scenario :
I have a project with budget amount lets say 10000$
i want to link employee with this project with percentage like employee Rami for example work 10% in project A and 25% in project B ANS SO ON . I WANT to make the salary from the budget of each project depending on the percentage i set
and i want a report to know the occupancy of each employee to know each employee free time
how i can make it using erpnext