Conditional sum with linked conditions in different tables

[ExcelStefan]

Hi!

I have two tables: one giving the link between a person and his job

Chelsea Architect
John Driver

and a second one, which says, who works in what week

John 1 1
Chelsea 1

I'd like to know, let's say, how many architects work in what week. In other words, I'd like to sum all the values of people, who are architects.

Does somebody have an idea, how to "make Excel know" that Chelsea is an architect?

Thanks!!