restrict access to see payroll

Hi there,
I am confused on finding the best way to restrict employees access to see other peoples salary that are on the same management level.  Say for example I need two managers to approve and see their subordinates payroll and time and expense info but not for anyone else how do i do this?  I know how to set up subordinates and then restrict a role by that but that still leaves the problem of the two managers seeing eachother's payroll info.

Any suggestions?

chris