your handles statement is missing the
handles Textbox2.TextChanged
Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
Note: This normally happens when you delete the control from the form, it removes the Handles event in the sub's header.
It should have something like this
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
End Sub