I have an Azure functions application (.net8, isolated model). There is a queue trigger working pretty good with internal application storage. It looks like this:

[Function(nameof(InnerStorageTrigger))]
public void InnerStorageTrigger([QueueTrigger("test-queue-inner")] QueueMessage message)
{
    _logger.LogInformation($"Inner message: {message.MessageText}");
}

But I also need another trigger, connected to an another storage account. I know I could keep the additional connection string in application settings (either local.settings.json or app configuration in Azure). But unfortunately the connection string comes from an external source and I can only access it in Program.cs. I tried to set an environment variable before initializing the host:

Environment.SetEnvironmentVariable("MyConnection", GetExternalConnectionString());

var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .ConfigureAppConfiguration((context, config) =>
    {
        config.AddEnvironmentVariables();
    })
    .Build();

host.Run();

The second trigger function:

[Function(nameof(TestQueueOuter))]
public void Run([QueueTrigger("test-queue", Connection = "MyConnection")] QueueMessage message)
{
    _logger.LogInformation($"From outer: {message.MessageText}");
}

It does not work. I’m getting an error: “The ‘TestQueueOuter’ function is in error: Microsoft.Azure.WebJobs.Host: Error indexing method ‘Functions.TestQueueOuter’. Microsoft.Azure.WebJobs.Extensions.Storage.Queues: Storage account connection string ‘AzureWebJobsMyConnection’ does not exist. Make sure that it is a defined App Setting.“.
I also tried to name the environment variable explicitly “AzureWebJobsMyConnection” – still no success.

So I’d like to know: How can I declare a queue trigger connected to an external storage account, with condition that I can only get the connection string in runtime?
Thank you in advance!