ExtJS focus Ext.form.Checkbox on tab

Inside a Ext.form.FormPanel I have few textboxes and three checkboxes, the tab index works correctly for the text boxes. Meaning when use presses tab the control moves to next text box.

But to control doesn't move to Ext.form.Checkbox within the form instead it goes else where.

Need a solution so that the control flows through all three Ext.form.Checkboxs and then out of the Ext.form.FormPanel

The following is a sample of what I have done:

        var frmAdv = new Ext.form.FormPanel({
            id: 'frmAdv',
            items: [{
                layout: 'column',
                bodyStyle: 'padding: 10px',
                //defaultType: 'lovcombo',
                items: [{
                    column: .5,
                    border: false,
                    width: 470,
                    items: [{
                        ----
                     filterShowIgnored, filterShowRejected, filterShowReport
                        ----
                    ]
                    }]
                }]
            }],


        var filterShowRejected = new Ext.form.Checkbox({
            boxLabel: 'Include rejected',
            id: 'chkRejected',
            enableKeyEvents: true
        });

        var filterShowIgnored = new Ext.form.Checkbox({
            boxLabel: 'Include ignored',
            id: 'chkIgnored',
            enableKeyEvents: true
        });

        var filterShowReport = new Ext.form.Checkbox({
            boxLabel: 'Include reported',
            id: 'chkReport',
            enableKeyEvents: true
        });

Thanks for any help