How do I COPY the selected text from a webBrowser page?

This is a Hard question(apparently simple):
How do I COPY the selected text from a webBrowser page, and paste it to a text file( for example)?
I have this until now:

private void webBrowser1_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
  {
//the 67 is the mousebutton no4 (I have 5 5buttons and a scrolwhell-A4Tech_X7 mouse)
//the mousebutton no4 is set to "ctrl+c" keys (Copy)
  if (e.KeyValue == 67)
  textBox2.Text=webBrowser1.DocumentText;
  }

Until now i cant manage to copy a text selection from webBrowser.
How to do that?
Thank you.