Totals not adding up correctly

Hello,

I would like to ask your help with the following problem. I am trying to calculate a YTD visit target for sales reps. Each sales rep has a visit target per week, and based on the selection of year and week in the slicers, the YTD total visit target should be calculated.

We distinguish three types of sales reps:

1. Employee started before the selected year and is still employed

2. Employee started within this year

3. Employee was employed at the beginning of this year but then quit

The formula has three different parts that account for the above three situations. The calculations lead to the right results on sales rep (employee) level. Yet, when calculating a total, the total doesn't add up. 

This issue is caused by part 2 and 3 of the formula. This because the calculation isn't done on the sales rep (employee) level but on the aggregate level. 

I am now looking for an option to calculate the visit target on the sales rep (employee) level and then add it all together. 

One of the things I've tried was to use "hasonefilter". Yet, this only works to calculate the values per sales rep (employee). It then seems to be impossible to sum these values. 

Could you please guide me in the right direction how to solve this issue?

YTD Visit Target = 
//part 1: employee is staying with the company
CALCULATE (
    SUM ( Employees[Target per Week] ),
    FILTER (
        Employees,
        AND ( Employees[Starting Year] < [Selected Year], Employees[Isactive] = "TRUE" )
    )
) * [Selected Week]

//part 2: employee is new to the company
    + (
        CALCULATE (
            SUM ( Employees[Target per Week] ),
            FILTER (
                Employees,
                AND (
                    Employees[Starting Year] = [Selected Year],
                    Employees[Starting Week] <= [Selected Week]
                )
            )
        )
            * (
                [Selected Week]
                    - CALCULATE (
                        SUM ( Employees[Starting Week] ),
                        FILTER (
                            Employees,
                            AND (
                                Employees[Starting Year] = [Selected Year],
                                Employees[Starting Week] <= [Selected Week]
                            )
                        )
                    )
            )
    )

//part 3 employee has left the company
    + IF (
        CALCULATE (
            SUM ( Employees[Ending Week] ),
            FILTER ( Employees, Employees[Ending Year] = [Selected Year] )
        ) < [Selected Week],
        (
            CALCULATE (
                SUM ( Employees[Target per Week] ),
                FILTER ( Employees, Employees[Ending Year] = [Selected Year] )
            )
                * CALCULATE (
                    SUM ( Employees[Ending Week] ),
                    FILTER ( Employees, Employees[Ending Year] = [Selected Year] )
                )
        ),
        CALCULATE (
            SUM ( Employees[Target per Week] ),
            FILTER ( Employees, Employees[Ending Year] = [Selected Year] )
        ) * [Selected Week]
    )