Firstly you need to be sure that you send something and receive something. You can put AfxMessageBox(TEXT("Received")); if ReadFile returns TRUE.
The code I wrote in the previous message will show (maybe) only one received character.
If you think the problem is your edit box you can play with it only. For example put a button on the dialog and write something like m_edText.SetWindowText(TEXT("ONE"));
or
if you know how to use the class wizard:
m_strEdit = TEXT("ONE");
UpdateData(FALSE);