Change downloaded XLS file name using exporterbutton

Hello ,



I want to download an Excel file of my grid. I am using an exporterbutton and its working fine , but i want to change my downloaded file name , Every-time the file name remains same (default file name : download.xls)



Here it is my code ,



tbar: [{



xtype: 'exporterbutton',

format: "excel",

fileName: 'Exporter',

title: 'User Report',

text : 'Export to XLS',

// downloadName : "download"

},

Change downloaded XLS file name using exporterbutton