Thanks Roger. I believe I have figured out a solution using an Imported SmartDL
We have an external source – currently a CSV file but in production it will be an Oracle DB.
The Source contains a row for each employee and has the employee number (emp_ID) along with his/her managers employee number (Mngr_ID)
In Active Directory we have the employee number in extensionAttribute2
I set up an Imported SmartDL and associate the key fields to be emp_ID and extensionAttribute2. I then modified the query on the database tab to be as follows:
Select [emp_ID] FROM [some_file.csv] WHERE Mngr_ID='AB123456'