How to restrict selection in forms based on selected data?


I have three tables Clients, Services & Volunteers

I have a form view on Services where volunteers select themselves as service providers and a specific client, assigned to them in the Volunteers table.

The problem is that when selecting a Client, all clients are exposed for selection, not just those assigned to the Volunteer.

Since lookups do not seem to display in forms, I am at a loss on how to achieve the goal of entering a Service record through a form, that specifies Volunteer and Client, but with exposing only the clients assigned to that Volunteer.

Any suggestion are most welcome,
Thank you