How to access the QAT context menu items in WinForms RibbonControlAdv?

ToolStripButton newItem = new ToolStripButton();
private void ribbonControlAdv1_BeforeCustomizeDropDownPopup(object sender, DropDownEventArgs e)
{
    newItem.Text = "New Item";
    e.DropDown.Items.Add(newItem);
    foreach (ToolStripItem ts in e.DropDown.Items)
    {
        this.listBox1.Items.Add(ts.Text);
    }
}

Private newItem As ToolStripButton = New ToolStripButton()
Private Sub ribbonControlAdv1_BeforeCustomizeDropDownPopup(ByVal sender As Object, ByVal e As DropDownEventArgs)
    newItem.Text = "New Item"
    e.DropDown.Items.Add(newItem)
    For Each ts As ToolStripItem In e.DropDown.Items
        Me.listBox1.Items.Add(ts.Text)
    Next ts
End Sub