Column ID based on another columns data.

I had 3 columns in a table Employee ID , Employee name & Manager name. I want to create a 4th column name as Managers ID which will come from Employee ID. Any help will be really appreciated.

This is what exactly i want :

EmployeeID   EmployeeName   Managername   ManagerID  

1                    ABC                      JHU                    4

2                    SDF                      MLP                    5

3                    BKJ                       ABC                    1

4                    JHU                      SDF                     2

5                    MLP                      SDF                    2