Extjs: Parsing value of combobox in tbar to the create-window form

MyCmp.combo.CategoryList = function(config) {
    config = config || {};
    Ext.applyIf(config, {
        name: 'category',
		hiddenName: 'category',
		displayField: 'name',
		valueField: 'id',
		fields: ['id','name'],
		forceSelection: true,
		typeAhead: true,
		editable: false,
		allowBlank: false,
		url: MyCmp.config.connector_url,
		baseParams: {
            action: 'mgr/categories/getList',
			combo: true
        }
    });
	
    MyCmp.combo.CategoryList.superclass.constructor.call(this, config);
};

Ext.extend(MyCmp.combo.CategoryList, MODx.combo.ComboBox);
Ext.reg('my-combo-categories', MyCmp.combo.CategoryList);

tbar: [{
	text: 'Create',
	handler: {
		xtype: 'my-window-create',
		blankValues: true
	}
},{
	xtype: 'tbfill'
},{
	xtype: 'my-combo-categories',
	name: 'categories',
	id: 'filter-category',
	emptyText: 'Category',
	value: MODx.request.category ? MODx.request.category : 1,
	allowBlank: false,
	width: 150,
	listeners: {
		'select': { fn: this.filterByCategory, scope:this }
	}
}]

MyCmp.window.CreateMessage = function(config) {
    config = config || {};
	
    Ext.applyIf(config,{
		title: 'Create message',
		url: MyCmp.config.connector_url,
		baseParams: {
			action: 'mgr/messages/create'
		},
		fields: [{
				xtype: 'textfield',
				fieldLabel: 'Name',
				name: 'name',
				width: 200,
				allowBlank: false
			},{
				xtype: 'textarea',
				fieldLabel: 'Message',
				name: 'message',
				width: 200,
				allowBlank: false
			}
		]
    });
	
    MyCmp.window.CreateMessage.superclass.constructor.call(this, config);
};

Ext.extend(MyCmp.window.CreateMessage, MODx.Window);
Ext.reg('message-window-create', MyCmp.window.CreateMessage);