Project Managers need to see the total cost based on the actual hours each user has worked on a project but these hours should not include the overtime hours (although they should be visible in the report). They should include only the scheduled hours (which the users are informed separately).
Create a User Defined Field at the Timesheet Hour Level. Name this UDF as Overtime. Then assign this UDF to all users of timesheet by enabling it in the timesheet permission profile.
Users should enter only the scheduled hours in the timesheet. If they had to work overtime for any project, they will enter those overtime hours only in the UDF provided.
Modify the Project Status Report to include the Total Hours, Overtime Hours (UDF), Hourly Cost and Cost Amount against a project. Here the total hours worked and the corresponding cost for the project which did not include the overtime hours will be visible at a project level. And the overtime hours will visible as well for reference purpose.