Firstly I am new to EXTJS and am stuck with this issue and no solution for weeks. Your help is much appreciated.

I have a grid with CheckboxModel. So a user can select x rows and click on button called "Update Status". This button should open a pop-up window with list of Statuses (Active, In-Active, Closed etc.) in a combobox and button for save and cancel. When user presses Save, update all selected rows/records with the selection value in the combobox, can close the window.
selModel: Ext.create('Ext.selection.CheckboxModel', {
listeners: {
selectionchange: function (sm, selections) {
Ext.ComponentQuery.query('#UpdateStatus')[0].setDisabled(selections.length == 0);