how to pick files 1 by 1 in html frames

Hi guys,

thanks in advance.....

i have one html form .this form has been splitted vertically as 2 parts by using html frames.


one frame for pdf files display,
another frame for excel files display


my task is ,


pdf folder having 100 pdf files.and,file names as 1.pdf,2.pdf,3.pdf.....etc.


excel folder having 100 excel files.file names as 1.xls,2.xls,3.xls.....etc.


In adition to as said earlier,html page also having one submit button under the page.


whenever we open html page .it will shows one side 1.pdf file and other side 1.xls file.
then this form should be replaced with 2.pdf and 2.xls when we click on submit button. 




Thanks
Ravi Gaddam