1.
// Displays the valueField after change
2.

3. {
    "name": "agency",
    "width": 172,
    "filterable": true,
    "editable": true,
    "header": "Agency",
    "editor": {
        "displayField": "display",
        "fieldLabel": "Agency",
        "xtype": "combo",
        "required": true,
        "blankText": "agency :",
        "hiddenName": "agency",
        "readOnly": false,
        "allowBlank": false,
        "mode": "local",
        "valueField": "id",
        "triggerAction": "all",
        "store": new Ext.data.SimpleStore({
            fields: ['id', 'display'],
            data: [
                [1, "BBDO"],
                [2, "Publicis"],
                [3, "Ogilvy & Mather NY"],
                [4, "Hill Holliday"],
                [5, "Standard Time"],
                [6, "Leo Burnett"]
            ]
        }),
        "name": "agency"
    }
    4.

    5.

    6.
    // Displays the displayField after change
    7. {
        "name": "status",
        "filterable": true,
        "editable": true,
        "header": "Status",
        "editor": {
            "displayField": "display",
            "fieldLabel": "Status",
            "xtype": "combo",
            "required": true,
            "blankText": "status :",
            "hiddenName": "status",
            "readOnly": false,
            "allowBlank": false,
            "mode": "local",
            "valueField": "id",
            "triggerAction": "all",
            "store": new Ext.data.SimpleStore({
                fields: ['id', 'display'],
                data: [
                    [0, "Completed"],
                    [1, "Not Started"],
                    [2, "Cancelled"],
                    [3, "In Progress"],
                    [4, "Paused"]
                ]
            }),
            "name": "status"
        },
        "renderer": function (v) {
            a = {
                "0": "Completed",
                "1": "Not Started",
                "2": "Cancelled",
                "3": "In Progress",
                "4": "Paused"
            };
            return a[v] || "";
        }
    },