VS 2010 - How To Split A String

I am able to populate a text box with a long string. This string is a collection of email addresses, I am wondering how I can split this string so that I am able to get the individual email addresses? If I select multiple email addresses it come through like Example: test1@test.comtest2@test.com in the one text box how could I split this so I could get test1@test.com in one text box and test2@test.com in another?

Code:

Protected Sub BtnEmailList_Click(sender As Object, e As System.EventArgs) Handles BtnEmailList.Click
' StringBuilder object
Dim str As New StringBuilder()

' Select the checkboxes from the GridView control
For i As Integer = 0 To GrdVwClassEmail.Rows.Count - 1
Dim row As GridViewRow = GrdVwClassEmail.Rows(i)

[Code].....