I am creating a course development spreadsheet. One sheet has a list of all
of the course developers and their contact information. A second sheet lists
all of the courses being developed.

I would to have a column in the first sheet (list of developers) that shows
which courses they have developed over time. For example, there is a column
in the second sheet (courses) where we identify in Column A the course ID
(e.g., BUS 280) and in Column K we identify the developer (e.g., Mary Smith).

In the second sheet, I'd like Column H to search the second sheet and find
every instance of courses, say, Mary Smith developed over time. So, the cell
in Column H might say

--BUS 280 or
--BUS 280, BUS 356, BUS 348 or
--some other combination

Is this possible? I know how to search for a single instance and return that
value using VLOOKUP, but I am not sure if

(1) you can search for multiple instances and
(2) can return all of those instances in some legible format (e.g.,
separated with a comma) in ONE cell

Thanks!!! You are all awesome with you clear and quick replies!!!