VS 2008 Forms - Tabs And Control Collection

Using vb.net 2008 Forms. I have a groupbox consisting of several textbox's and a push button. I put this groupbox in a control collection in order to validate each texbox when the push button is clicked.

The code to do this is as follows:
Private Sub bn_updateadditem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bn_updateadditem.Click
Dim InvalidInput As Boolean = False
Controls.AddRange(New System.Windows.Forms.Control() {Me.GroupBox1})
Dim ctrl As Control
For Each ctrl In Controls
[Code] .....

This worked great. However when I moved this groupbox with all its controls onto a tab, the groupbox contents disappeared from the form after the control collection is created and contents validated (per above code).