To start, you'll need a third table for assigning staff to a specific request.
The data that you'd need to use to generate the above example would come from this Staff_Request table.
It gets more complicated from there.
How would it work with the following table instances:
Requests, Staff, Agencies
I want one given request which allows an agency to accept, decline or tentative a request that has been entered for a client.
The aim is to have a conditional value list on the requests layout so when an Agency 1 from dropdown is selected, the staff dropdown next to it would only show staff members in Agency 1. This is kind of, off topic from the orginal forum post/question - sorry. It's somewhat relevant.
I can't get my head around the relationships for this one.
Agencies would be linked to staff in a one to many relationship Agencies---<Staff-----<Staff_requests
Agencies::__pkAgencyID = Staff::_fkAgencyID
but in order to set up a basic conditional value list in which selecting an Agency filters a value list of staff down to just staff associated with that agency, you'd need an additional occurrence of Staff.
Staff_Requests::_fkAgencyID = Staff|VL::_fkAgencyID
You can then set up a value list that lists values from Staff|VL, include only related values starting from Staff_Requests
For more about conditional value lists, see "Adventures in FileMaking #1 - conditional value lists" for examples of 10 different ways to set up a conditional value list, including a basic conditional value list like the one set up here.