file upload value loses when pressing any buttun on form

Question

Sir,

 

 

I m using fileupload control in one of my asp.net web page creating using vb.

 

i have to validate age enterd by user with respect to another text field when this condition match it give some message to user. on button click.

At that  time, Value of fileupload control automatically lost so user need to re brose the file again.

So tell me how to prevent fileupload control value not to lose untill final submission.

 

Regards,

 

Vishal