GuiRollupCtrl Callback Help!

I have created a widget with a guiRolloutCtrl contained with in it. I was wondering if anyone knew what function is called for this when the triangle is pressed to roll-it-up, or un-roll it. Any help will be appreciated.

Thansk in advance.

%base = new GuiRolloutCtrl(baseCtrl) 
   {
      canSaveDynamicFields = "0";
      Profile = "EditorRolloutProfile";
      HorizSizing = "width";
      VertSizing = "height";
      Position = "0 0";
      Extent = "200 450";
      MinExtent = "8 2";
      canSave = "1";
      Visible = "1";
      hovertime = "1000";
      Caption = "Object Properties";
      Margin = "6 4";
      DragSizable = false;
      DefaultHeight = "100";
};