How to add a field in the form when a button is clicked

[arafat_alam]

I have a form panel and a button.i want to add a field in the form when the button is clicked..here is the model

Ext.regModel('Contact', {
    idProperty: 'id',
    fields: [
        { name: 'name', type: 'string' },
        { name: 'phone', type: 'string' },
        { name: 'email', type: 'string' },
        { name: 'address', type: 'string' },
    ],
    validations: [
        { type: 'presence', field: 'name', message: 'Please Enter A Contact Name' },
        { type: 'format', field: 'phone', message: 'Please Enter Phone Number', matcher: /[0-9]/ }
    ]
});

and here is the form

AddressBook.views.contactEditor = new Ext.form.FormPanel({    id: 'contactEditor',
    items: [
        {
            xtype: 'textfield',
            name: 'name',
            label: 'Name',
            required: true
        },
        {
            xtype: 'textfield',
            name: 'phone',
            label: 'Phone',
            required: true
        },
        {
            xtype: 'emailfield',
            name: 'email',
            label: 'Email'
        },
        {
            xtype: 'textareafield',
            name: 'address',
            label: 'Address'
        },        
    ],
    dockedItems: [
        AddressBook.views.contactEditorTopToolbar,
        AddressBook.views.contactEditorBottomToolbar,
        
    ]
});

i want another phone field in the form when a button is clicked....can any one help..please??