HTTP File Upload

Can someone please let me know how this can be done ?

a. Create a file stored on a particular folder on the server

b. Allow this file to be created,uploaded, downloaded, edited and uploaded back again .

c. Define this filename as an amalgam of the date+userid+record id to prevent it from getting overwritten each time?

The Issue:

I have a 2 types of files :a doc and an excel sheet.
File.doc is created by User1 and must be updated by User 1 and/or User 2
File.xls is created by User 2 and can be modified by User 3 but only read by User1.

I use a db but I do not know how to define in a table field the location of the files on the server nor how they can be accessed.

For example,

The php file created would have the foll. code :
Code:

$sql = Insert into Report (Userid, Date, Location,Reportid) VALUES ($userid, $date, $loc, $rid)

My big problem : How do i tell $loc that the value it needs to store in the table is = http://www.example.com/qnaire/mycompany/myproduct.doc

Thanks so much !
Swati

make them choose the folder when they upload it (then store the folder they selected) from there its pretty simple or ?

that would mean the folders would have to be predefined...do-able but the rest of the issues remain.