First, to identify the Jargon:
This is called a conditional value list. You can sear your training materials for any info on this term that might be present.
There are two ways to set this up:
One method uses a calculation field and permanently specifies a specific subset of the values. If you want only Staff marked as Managers and never any other group of values from the staff table to appear in the value list, this is the simplest option to use.
A second method uses a relationship to filter the values to a specific subset. Since a relationship matches values in 1 or more pairs of match fields, this option can allow you to match to different subsets of values by specifying a different value in one of the match fields. If you want the user to select "managers" in one field in order for a value list in a second field to list only managers, this option should be used.
See this thread for a tutorial on both Options 1 and 2: Custom Value List?
Thank you, again! :-)
As my Dad always said; "The Question's in the Answer." :-O