Event for second dialog box not working

Hello all,

I am using one dialogbox and on valueHelpRequest of that m triggerring a fragment but confirm and close method of that fragement is not getting triggered in controoler please help...My code as below

var dialog = new sap.m.Dialog({

title: 'Cost Center',

type: 'Message',

content: new sap.m.Input({

showValueHelp : true ,

valueHelpOnly: true,

valueHelpRequest : function(oEvent)

{

this.dlrcd = sap.ui.xmlfragment("com.altimetrik.zkb21n.view.dlrcd",this);

_thisView.addDependent(this.dlrcd);

this.dlrcd.setModel(sap.ui.getCore().getModel("approveModel"),"approveModel");

this.dlrcd.open(oEvent);

},

}),

beginButton: new sap.m.Button({

text: 'OK',

press: function () {

dialog.close();

}

}),

afterClose: function() {

dialog.destroy();

}

});

dialog.open();

I am calling dlrcd fragement..please help.