ATTR_VISIBLE for child panels

Hi,

Is there an attribute or a way that I can check to see if a child panel is displayed using DisplayPanel(..)?  It would seem that ATTR_VISIBLE for GetPanelAttribute(...) doesn't do quite what I want, as that attribute is set to 0 even if the child panel is displayed but isn't the panel shown on the screen (like for example, if the child panel is displayed on a tab that's not the currently selected tab, then ATTR_VISIBLE is set to 0).  Thanks.