basic wxpython help

[Vamp4L]

Hello,
  I'm brand new to wxpython, trying to implement some code to add rows
in the GUI dynamically.  What I want to do is when you click on the
Add Row button, a new row gets added after the first row, before the
button.  This code adds a row in the right place, but it overlaps the
button because it doesn't shift the button down.  Here's what I have
so far:

class TestPanel(wx.Panel):
    def __init__(self, parent, log):
        self.log = log
        wx.Panel.__init__(self, parent, -1)

        fgs = self.fgs = wx.FlexGridSizer(cols=1, hgap=10, vgap=10)

        fgs.Add(wx.StaticText(self, -1, "Label 1"))
        a1a = self.a1a = wx.FlexGridSizer(cols=5, hgap=10, vgap=10)
        fgs.Add(a1a)
        a1a.Add(wx.StaticText(self, -1, "User:"))
        cc = wx.Choice(self, -1, choices=["A", "B"])
        a1a.Add(cc)

        cc = FileSelectorCombo(self, size=(250, -1))
        a1a.Add((10,10))
        a1a.Add(wx.StaticText(self, -1, "Path:"))
        a1a.Add(cc)

        b = wx.Button(self, -1, "Add Row", (50,50))
        self.Bind(wx.EVT_BUTTON, self.OnButtonIE7, b)
        fgs.Add(b)

        box = wx.BoxSizer()
        box.Add(fgs, 1, wx.EXPAND|wx.ALL, 20)
        self.SetSizer(box)

        a1 = wx.FlexGridSizer(cols=5, hgap=10, vgap=10)
        fgs.Add(a1)
        b = wx.Button(self, -1, "Run Report", (50,50))
        self.Bind(wx.EVT_BUTTON, self.OnButtonRun, b)
        a1.Add(b)

        b = wx.Button(self, -1, "Close", (50,50))
        self.Bind(wx.EVT_BUTTON, self.OnButtonClose, b)
        a1.Add(b)


    def OnButtonIE7(self, evt):
        self.a1a.Add(wx.StaticText(self, -1, "Label 1"))
        self.a1a.Layout()

    def OnButtonRun(self, evt):
        wx.StaticText(self, -1, "User:")

    def OnButtonClose(self, evt):
        dlg = wx.MessageDialog(self, "Are you sure you want to exit?",
"Exit", wx.YES_NO | wx.ICON_QUESTION)
        if dlg.ShowModal() == wx.ID_YES:
            self.Destroy() # frame
            sys.exit(1)
        dlg.Destroy()

Any suggestions?
Thanks!