Save in extjs editor grid

Hi all,

I have created a VF page using extjs. It displays a an editable grid with values from object created in salesforce.

Now , what I want to do is save the changes made in the editable fields. Right now whatever changes I make in the editable fields are not saved. I want the modified records to be saved in store as well be updated in salesforce.Please help.....

Here is my vf page:

   <apex:page Controller="ProjectGrid">
   <link rel="Stylesheet" type="text/css" href="{!$Resource.ExtJs}/extjs/resources/css/ext-all.css" />
    <apex:includeScript value="{!$Resource.ExtJs}/extjs/adapter/ext/ext-base.js"/>
    <apex:includeScript value="{!$Resource.ExtJs}/extjs/ext-all.js"/>
    <script>

    Ext.onReady(function(){

   var buttonHandler = function(button,event) {

                   alert("Button 1 is Clicked");
                   };
        var button1 = new Ext.Button({applyTo:'m',text:'Button 1',handler:buttonHandler});
    var myDataString = 'var empGridRec = [ ';
           <apex:repeat value="{!proj}" var="con" >
           myDataString += "['{!con.Id}','{!con.Name}','{!con.Objective__c}','{!con.Description__c}','{!con.Start_date__c}'],";
           </apex:repeat>
           myDataString += "['','',''] ];";
           eval(myDataString);


    var store = new Ext.data.ArrayStore({

    fields : [

    { name: 'ID' },

    { name: 'Name' },

    { name: 'Obj' },

    { name: 'Desc' },

    { name: 'date' }


    ]

    });

    store.loadData(empGridRec);

    var empColumnModel = new Ext.grid.ColumnModel ({
    columns:

    [{
      id:'ID' ,
    header: 'Employee Number',

    readOnly: true,

    width: 100,

    sortable: true,

     editor: true


    },

    {
     id:'Name',
    header: 'Name',

    readOnly: true,

    width: 150,

    sortable: false,
     editor: true

    },

    {
      id:'Obj',
    header: 'Designation',

    readOnly: true,

    width: 100,

    sortable: true,


     editor: true

    },
     {
      id:'Desc',
    header: 'Designation',

    readOnly: true,

    width: 100,

    sortable: true,

     editor: true

    },

    {
      id:'date',
    header: 'Salary',

    readOnly: true,

    width: 75,

    sortable: true,



    editor: new Ext.form.NumberField({

    allowDecimals: true

    })

    }]

    });

    var empGrid = new Ext.grid.EditorGridPanel({

    store: store,
        cm: empColumnModel,
        renderTo: 'm',
        width: 600,
        height: 300,
         title: 'ABC',
        frame: true,
        items:button1,
        clicksToEdit: 1
       );


    });
   store.load();

    });

    </script>
<div id="m">
</div>

    </apex:page>