I want to invoke one or several functions (depending on user choices) when a "3DArea" tab is selected/clicked.
eg An_US_SUMlev() & An_JAP_SUMlev() (NB functions need to be listed in "stacked" format rather than all on one line)
The code below achieves this but I am getting "Error on Page" messages in IE8 ("Object does not support this object or method") but not other browsers !

But when the functions are invoked manually via a simple button instead i get NO IE8 errors !!?
(this suggests function codes is OK - so no function code shown here)  Why ?

Any simple way to elimanate these error messages in IE8 by tweaking jquery tab coding below ?
Or can this PARTICULAR error be suppressed in IE8 ?
(Any sources of more general info on jquery active tabs & events syntax ?)

Thanks

1. 
    // Global tabs variable
    var tabs;
    $(document).ready( function() {
    // global var win to store the ExtJs html element
    // basic tabs 1, built from existing content
    if(!tabs)
    tabs = new Ext.TabPanel({
    renderTo: 'tabs1',
    width:1000, activeTab: 0, frame:true, defaults:{autoHeight: true}, items:[
    {contentEl:'2DArea', title: '2D Chart(s)'},
    {contentEl:'3DArea', title: '3D Chart(s)',
    onClick: An_US_SUMlev(),
    onClick: An_JAP_SUMlev()
   
   
   
   
   
   
   
   
   
   
   
   
   
2.  },
    {contentEl:'Description', title: 'Details'}
    ]
    });