extjs how to determine active tab in a tab panel

Ext.onReady(function(){    
    var memberModel = [
        {name:'COMPANY',mapping:'COMPANY'},
        {name:'CITY',mapping:'CITY'},
        {name:'SYSTEM',mapping:'SYSTEM'},
        {name:'CID',mapping:'CID',type:'int'},
        {name:'CWEB',mapping:'CWEB'},
        {name:'COMPANYTYPE',mapping:'COMPANYTYPE'},
        {name:'ACOMPANYLASTDATE',mapping:'ACOMPANYLASTDATE'},
        {name:'ACOMPANYLASTUSER',mapping:'ACOMPANYLASTUSER'}
    ];
    var pmReader = new Ext.data.CFQueryReader({id:'COMPANY'},memberModel);
    var pmStore = new Ext.data.Store({
        url:'cfc/ext.cfc',
        baseParams:{method: 'getPMembers',returnFormat: 'JSON',queryFormat: 'column'},
        reader: pmReader,
        sortInfo: {
            field: 'COMPANY',
            direction: 'ASC'
        }
    });	
	pmStore.load();
    var ceoModel = [
        {name:'COMPANY',mapping:'COMPANY'},
        {name:'LAST',mapping:'LAST'},
        {name:'FIRST',mapping:'FIRST'},
        {name:'TITLE',mapping:'TITLE'},
        {name:'EMAIL',mapping:'EMAIL'},
        {name:'COMPANYTYPE',mapping:'COMPANYTYPE'},
        {name:'ADDRESS',mapping:'ADDRESS'},
        {name:'CITY',mapping:'CITY'},
        {name:'STATE',mapping:'STATE'},
        {name:'ZIP',mapping:'ZIP',type:'string'},
        {name:'PHONE',mapping:'PHONE'},
        {name:'FAX',mapping:'FAX'}
    ];
    var ceoReader = new Ext.data.CFQueryReader({id:'COMPANY'},ceoModel);
    var ceoStore = new Ext.data.Store({
        url:'cfc/ext.cfc',
        baseParams:{method: 'pMemberCeos',returnFormat: 'JSON',queryFormat: 'column'},
        reader: ceoReader,
        sortInfo: {
            field: 'COMPANY',
            direction: 'ASC'
        }
    });	
	ceoStore.load();
    var viewport = new Ext.Viewport({
        layout: 'border',
        id: 'pmViewport',
        renderTo: Ext.getBody(),
        items: [{
            region: 'north',
            id: 'pmToolbar',
            xtype: 'toolbar',
            items: [{
               xtype: 'tbspacer'
            },{
                xtype: 'tbbutton',
                text: 'Excel',
                handler: function(){
                    alert('Go to Excel');
                }
            },{
                xtype: 'tbfill'
            }]
        },{
            region: 'west',
            id: 'pmNewarea',
            xtype: 'panel',
            split: true,
            width: 250,
            margins: '0 0 0 5',
            html: 'West'
        },{
            region: 'center',
            id: 'pmGridarea',
            xtype: 'tabpanel',
            activeTab: 0,
            items: [{
                xtype: "grid",
                store: pmStore,
                autoExpandColuumn: 'COMPANY',
                sm: new Ext.grid.CellSelectionModel({
                        listeners: {
                            cellselect: function(sm, iRow, iCell){
                                if(iCell == 4){
                                    var d = sm.grid.selModel.selection.record.data;
                                    if (d.CWEB != null && iCell==4) {
                                        var url = "http://" + d.CWEB.substr(0,d.CWEB.indexOf('<'));
                                        //alert(url);
                                        var wname = 'companyWeb';
                                        var wfeatures = 'menubar=yes,resizable=yes,scrollbars=yes,status=yes,location=yes';
                                        window.open(url,wname,wfeatures);
                                    }
                                }
                            }
                        }
                    }),
        		columns: [
                    {id: "member",  header: "Member",       dataIndex: 'COMPANY',           sortable: true,     width: 250},
                    {id: "city",    header: "City",         dataIndex: 'CITY',              sortable: true},
                    {id: "system",  header: "System",       dataIndex: 'SYSTEM',            sortable: true,     width: 200,   tooltip: 'The Healthcare System this company belongs to'},
                    {id: "cid",     header: "ID",           dataIndex: 'CID',               sortable: true, hidden: true},
                    {id: "web",     header: "Web Site",     dataIndex: 'CWEB',              sortable: true,     width: 150},
                    {id: "type",    header: "Company Type", dataIndex: 'COMPANYTYPE',       sortable: true},
                    {id: "update",  header: "Last Update",  dataIndex: 'ACOMPANYLASTDATE',  sortable: true, hidden: true,     renderer: Ext.util.Format.dateRenderer('m/d/y')},
                    {id: "user",    header: "Last User",    dataIndex: 'ACOMPANYLASTUSER',  sortable: true, hidden: true}
        		],
                title: 'Members'
            },{
                xtype: "grid",
                store: ceoStore,
                autoExpandColuumn: 'COMPANY',
        		columns: [
                    {id: "member",  header: "Member",       dataIndex: 'COMPANY',       sortable: true, width: 250},
                    {id: "last",    header: "Last",         dataIndex: 'LAST',          sortable: true},
                    {id: "first",   header: "First",        dataIndex: 'FIRST',         sortable: true},
                    {id: "title",   header: "title",        dataIndex: 'TITLE',         sortable: true, width: 150},
                    {id: "email",   header: "Email",        dataIndex: 'EMAIL',         sortable: true, width: 150},
                    {id: "type",    header: "Company Type", dataIndex: 'COMPANYTYPE',   sortable: true},
                    {id: "address",    header: "Address",   dataIndex: 'ADDRESS',       sortable: true, hidden: true}, 
                    {id: "city",    header: "City",         dataIndex: 'CITY',          sortable: true, hidden: true}, 
                    {id: "STATE",   header: "STATE",        dataIndex: 'STATE',         sortable: true, hidden: true},
                    {id: "zip",     header: "ZIP",          dataIndex: 'ZIP',           sortable: true, hidden: true},
                    {id: "phone",   header: "PHONE",        dataIndex: 'PHONE',         sortable: true, hidden: true},
                    {id: "fax",     header: "FAX",          dataIndex: 'FAX',           sortable: true, hidden: true}
        		],
                title: 'Member CEOs'
            }]
        },{
            region: 'east',
            id: 'pmEditarea',
            xtype: 'panel',
            split: true,
            width: 250,
            margins: '0 5 0 0',
            html: 'East'
        },{
            region: 'south',
            id: 'pmStatusarea',
            xtype: 'panel',
            margins: '0 5 5 5',
            html: 'South'
        }]
    });
});
                              

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