Can I populate a Select field based on an API call made when editing an item in a collection?

I have a "Users" collection where every user has an additional internal ID. I want to make a call to an external API with that ID and populate the items of a select field based on the response. I think this is do-able, but I'm blanking on how 😄

I'm thinking of using afterRead?

    {
      name: 'events',
      maxDepth: 0,
      type: 'relationship',
      relationTo: 'events',
      hasMany: true,
      access: {
        create: () => false,
        update: () => false,
      },
      admin: {
        readOnly: true,
      },
      hooks: {
        beforeChange: [({ siblingData }) => {
          // Mutate the sibling data to prevent DB storage
          // eslint-disable-next-line no-param-reassign
          siblingData.events = undefined;
        }],
        afterRead: [getAllEvents],
      },
    },

But im not sure why we need to mutate the sibling data

or if that was only for that example

Hmmm that runs on every item in the collection

Was hoping for it to run only during editing

Do you think I'm going about it incorrectly?