Ext.js trying to transform a dropdown list into two a checkboxgroup with store handler

I have the following code:

{
                xtype         : "combobox",
                fieldLabel    : "Content type",
                labelAlign    : fx.consts.formAlignment,
                //listeners     : fx.utils.appendTooltip("Replication", "How many copies to keep for each video file for this group"),
                name          : "content_type",
                id            : "fx-form-content_type",
                value         : 0,
                store         : Ext.create("Ext.data.Store", {
                    fields: ["text", "value"],
                    data  : [
                        {
                            text : "All",
                            value: 0
                        },
                        {
                            text : "VOD",
                            value: 1
                        },
                        {
                            text : "NPVR",
                            value: 2
                        }
                        {
                          text:"None"
                          value:3
                        }
                    ]
                }),
                editable      : false,
                forceSelection: true,
                queryMode     : "local",
                displayField  : "text",
                valueField    : "value}

When I click on the dropdown list it shows these 3 options. With the store :Ext.create("Ext.data.Store",... when I press some option from these I get it stored in my object, now instead of this I want to have two chekboxes with names VOD , NPVR.

I can check both checkboxes, or just one of them or none. But I want the checkboxes to store the value which was before connected between text and value in the store section.