Slicer showing all values and not table specific values

[StuartSmith]

As an example, I have 2 tables, similar to below...

Master Lookup

Region	Country	City	Building	Staff
EMEA	UK	London	LON01	35
EMEA	France	Paris	PAR01	32
APJ	New Zealand	Christchurch	CHR01	6
AMER	US	Washington	WAS01	15

Absentees

Staff ID	Days Absent	Building
1	10/10/2022	LON01
1	11/10/2022	LON01
3	15/11/2022	LON01
4	30/11/2022	WAS01

The tables have a relationship between "Building".  I then have a slicer called Region using the Master Lookup Region column.  How can I get the slicer to only show th regions associated with the "Building" column from the "Absentee" table?  So the Region slicer would only have EMEA & AMER, as currently th slicer is showing all regions.  Hope that makes sense and thanks in advance.   

[StuartSmith]

Added example file. Example pbxi file 

[bolfri · Accepted solution]

Create a measure:

HasRows = COUNTROWS(Absentees)

and put it on filter with "is not black" rule on slicer.

[StuartSmith]

That worked great, but then noticed an issue that if the slicers are synced across multiple tabs, the "HasRows" filter is synced as well.  So I have a "Region" slicer on "Report 1" and "Report 2" and if I select "EMEA" from the "Region" slicer, it filters "EMEA" across both "Report 1" and "Report 2". Just as expected, but I need "HasRows CUser Data = COUNTROWS('Cuser data')" on "Report 1" Region Slicer and "HasRows Absentees Data = COUNTROWS('Absentees data')" on "Report 2" Region slicer.  

I hope that makes sense.

[StuartSmith]

Looks like I found the solution...