Additional filter on TreatAs limiting Values

Hi gghlyon ,

You can follow the steps below to get it:

1. Create a slicer base on the field 'ENGINEER'[Dept]

2. Create a measure as below to get Rocketry Hours 

Rocketry Hours =
VAR _depts =
    ALLSELECTED ( 'ENGINEER'[Dept] )
VAR _engineers =
    CALCULATETABLE (
        VALUES ( 'ENGINEER'[FullName] ),
        FILTER ( 'ENGINEER', 'ENGINEER'[Dept] IN _depts )
    )
RETURN
    CALCULATE (
        SUM ( 'TICKET'[ActualHours] ),
        FILTER ( 'TICKET', 'TICKET'[HelpdeskEmployeeName] IN _engineers )
    )

If the above one can't help you, please provide some raw data in your tables 'ENGINEER' and 'TICKET' (exclude sensitive data) with Text format and your expected result with backend logic and special examples? It would be helpful to find out the solution. You can refer the following links to share the required info:

How to provide sample data in the Power BI Forum

How to Get Your Question Answered Quickly

And It is better if you can share a simplified pbix file. You can refer the following link to upload the file to the community. Thank you.

How to upload PBI in Community

Best Regards