Welcome to the forums!
OK, if you want to upload excel documents onto your website for people to download onto their local PC, I would highly recommend zipping them (exceldocs.zip). This will compress them for faster download. You can download winzip from
http://www.winzip.com/
As for the download manager, you woudl either have to program the entire script yourself or do a search in
Google or check out
HotScritps
Good luck!