multiple textboxes created dynamically

Question

 I have my roots in pascal like languages and just recently started in c# and OOP
I can manage my way around, but I just am missing a key point, so I hope you can help me.

ps. I am using Microsoft Visual C# 2008 expressedition

I was building a text editor as an exercise.
I do not create the textbox at design time, but do it dynamically when I click the menu option, open file.
so far all fine. I also created a menustrip and items among which "window" and when I click open, the filename that I open is added to the menustrip under window

So : the textwindow is opened by the method below:

private void openToolStripMenuItem_Click(object sender, EventArgs e)
{
      openFileDialog1.InitialDirectory = @"d:\";
      openFileDialog1.Filter = "Text files (*.txt)|*.txt|All files (*.*)|*.*";
       DialogResult myfile = openFileDialog1.ShowDialog();
      TextBox txt = new TextBox();
      txt.Multiline = true;
      txt.Location = new Point(5, 25);
      txt.Width = this.Width -20;
      txt.Height = this.Height - 64;
      txt.Lines = File.ReadAllLines(openFileDialog1.FileName);
      Controls.Add(txt);
      this.windowToolStripMenuItem.DropDownItems.Add(openFileDialog1.FileName);
}

this works OK for the first txt file I open, but if I then open another file, it does show up under window as a second entry, but the textbox itself is not showing up....

and my other issue is, txt is unknow to other methods. so say I click on one of the entries under window how do I know which txt window to make the "active" window ?
I would assume to make a class that holds the window handle, filename and maybe more and then an array of this class. every array[1] contains a copy of this class so I can relate an entry from the "window" drop down to a handle, but how can every method access this array (or whatever you would suggest to create)