Asp.net - User Enters Code Into TextBox, Code Gets Added To URL (using Session)?

I'm using ASP.net 4.0 VB,I am using a session variable to add a user entered code into the url of each page. I can get the code to show up at the end of the page's URL that my textbox is on, but what do I add to every page to make sure that the session stays at the end of every URL that person visits during their session? This is the code from the page that the user enters their user code.

Protected Sub IBTextBoxButton_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles IBTextBoxButton.Click
Session("IB") = IBTextBox.Text
Dim IB As String = Session("IB")
End Sub

[code]....

This is what I have in the page load of one of the other pages. What else do I add to make sure that variable is added to the URL of that page?

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim IB As String
IB = Session("IB")
End Sub