FileUpload control lossing selected after postback

Hi guys,
 
I am facing an issue with FileUpload Control in ASP.Net 3.5.
 
I selected a file in FileUpload and in the same page there is a checkbox and which is causing postback on selected index changed. and on postback Fileupload is losing selected file.
 

I tried by using updatepanel and write the check box area in Update panel. but page is still cauisng postback.
 

Any help or suggestion will be appreciated.
 
Anything need to know more about this issue, please gimme a shout .
 
thanks.