How do I create a measure that references two different tables

Everything I've had to do thus far for things like this was to get the tables merged into a singular query.  Manipulate the date info, so that it's supportive of an employee record etc.  I haven't been able to have like what you wanted (and I did too) which was to have multiple different queries and have a slicer affect them all.  The way I solved this was to create modular queries that worked as autonomous tables, and then a set of queries that built joins upon those "atomic level" queries.  Then I could get the visuals to all filter nicely.

hope it helps.