[Noobie] Forms and Changing Form Values

Sorry for the noobie question, but I'm having a lot of trouble going through the MSDN files and finding the solution to this.

So I have a very basic form I made in VS2005 Express.  The form consists of 12 text boxes and that's it (I'm starting out basic to learn this).  If I have a constant stream of data (Think stock prices, constantly coming in and constantly changing) how do I get one of the textboxes to change every time that value changes?

So lets say that my constant stream of Data was a DoubleSeries

so ...

DoubleSeries DSeries = new DoubleSeries;
//Do a bunch of code to populate DSeries

public partial class Form1 : Form

{
public Form1()
   {
    InitializeComponent();
   }
}



So now where do I go from here.  is it ...

TextBox1.Text = DSeries.Last.ToString();

OR

Do i have to use an eventHandler to populate the textbox every time DSeries.Last changes?

Thanks!