Updating combobox if the ToString() result of an item changes

Hello,
I've got a simple question related to combobox. Consider that a combobox is populated with the instances of the following example class:

class Plot
{
  private string label;

  public string Label
  {
    get { return label; }
    set { label = value; }
  }

  public override string ToString()
  {
    return label;
  }
}

Now consider that one of these objects will be assigned a different label somewhere else in the program. How can I notify the combobox that it should call the ToString() method of this item again to update its list accordingly? I hope there exists some intelligent mechanism, I'd like to avoid just manually repopulating the combobox each time an item label is changed.