Creating a measure based on a column from another linked table

I have 2 tables linked together: Employee table and Sales Order table (1:many relationship using Employee ID key and Created by Employee ID key)

I want to create a measure in Sales Order table that count number of sales order quantity created by people from Asia office.

so in the second table, sales document number 111,114,115 are created by employee 001 and 003 and they are all from Asia office according to the Employee table. The result should be 50+100+50 = 200