In C#; what is the most efficent way to check for changes from a background thread?

I create a thread for each of my network communications and they add to a list responses whenever they hear back from a client. I'm starting up the task below at execution to see if any communications come in. It displays the most recent one on screen.

Task task = new Task(
(() =>
 {
    int i = 0;
    while (true)
    {
        if (responses.Count > i){
            Debug.WriteLine(responses[i]);
            int index = Form.ActiveForm.Controls.IndexOfKey("responseBox");
            Form.ActiveForm.Invoke((MethodInvoker) (() => Form.ActiveForm.Controls[index].Visible = true));
            Form.ActiveForm.Invoke((MethodInvoker) (() => Form.ActiveForm.Controls[index].Text = responses[i]));
            i++;
        }
    }
 }));
task.Start();

My question is; is there a better way for me to do this? It seems wrong to me to have the task constantly working for something that doesn't happen very often.

Edit: I'm very new to C#, so if there's something obvious please don't hesitate to point it out.

Update:

As per the nice tutorial from MS that sidewinder linked I added a simple event to the Add function of List. as So:

public delegate void ChangedEventHandler(object sender, EventArgs e);

public class listWithChanges<T> : List<T> 
{
    public event ChangedEventHandler Changed;

    protected virtual void OnChanged(EventArgs e)
    {
        if (Changed != null)
            Changed(this, e);
    }

    public new void Add (T item)
    {
        base.Add(item);
        OnChanged(EventArgs.Empty);
    }
}

and added to my output with a delegate

responses.Changed += ((o, e) => {
                                int index = Form.ActiveForm.Controls.IndexOfKey("responseBox");
                                Form.ActiveForm.Invoke((MethodInvoker) (() => Form.ActiveForm.Controls[index].Visible = true));
                                Form.ActiveForm.Invoke((MethodInvoker) (() => Form.ActiveForm.Controls[index].Text = responses[responses.Count - 1]));
                              });