Find the difference of Employee and manager salaries using MDX

Question

I have a Dimension with attributes Employee Number, Manager Number. Measure called Salary.

I need to display employee number , his/her Manager number and Salary difference.

sample data like below.
EmpNo - ManagerNo - Salary
1 - 0 - 10000
2 - 1 - 8000
3 - 2 - 7000
4- 0 - 12000

expected output as
EmpNo-ManagerNo-Diff.in Salary
1 - Not available - 10000
2- 1 - 2000
3 - 2 - 1000
4 - Not available - 12000

If no manager means we can show same salary. Could you please guide me how to achieve this using MDX.

Thank you for any support.