Can not get a fieldset event "active" listener to work...

Basically and I have 2 fieldsets and wanna disable one if the otherone is selected.
I've try activate, beforedeactivate and nothing

afterrender does work tho :-)


Code:
xtype:'fieldset',
                    id:'rootFieldset',
                    checkboxToggle:true,
                    title: 'Create a New Database (Roor Access Needed)',
                    defaultType: 'textfield',
                    collapsed: true,
                    layout: 'anchor',
                    defaults: {
                        anchor: '100%'
                    },
                    items :[{
                        fieldLabel: 'Database Host',
                        name: 'dbHost',
                        allowBlank:false
                    },{
                        fieldLabel: 'Database Port',
                        name: 'dbPort'
                    },{
                        fieldLabel: 'Root User',
                        name: 'rootUser'
                    }, {
                        fieldLabel: 'Root Password',
                        name: 'rootPass'
                    }],
                    listeners: {
                             activate: function(){
                               Ext.Msg.alert('Status', 'TEST!!!.');

                            //Ext.getCmp('dbuserFieldset').disable();
                            //Ext.getCmp('rootFieldset').enable();
                           }
                      }