VS 2005 - FileStream Storage Across Forms

I have a button on form 1. When the button is clicked, form 2 pops up. Form 2 also has a button.

Code for form 1:
Imports System.IO
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim textfile As New FileStream("textfile1.txt", FileMode.Create, FileAccess.ReadWrite)
Dim txtfilewriter As New StreamWriter(textfile)
[Code] .....

Now, as you see, on the form 1 load event, the streamwriter writes "Physics" to the text file. When the button on form 2 is clicked, the streamwriter writes "English" to the same file. As an end result, I expected BOTH "Physics" and "English" to be in the text file but the final result is only "English" in the text file. What do I have to do so that the textfile continuously stores these lines?