UPLOAD PROCEDURE RUNS UP AGAINST "PERMISSION DENIED"

I have access to a folder on a server and I am running my website from there.
I can access the site with ftp, even eith a line in the address bar of IE
ftp://username:password@theremoteserver.com

I have used this access to download the appropriate files to set up an ASP upload facility. (It works fine when tested on my local machine).
When I go to the URL and try to upload the file I get "Permission Denied".
Unfortuantely I have no ability to change permissions (nor can I contact the server administrator - along story, and legal!).

Surely there is some way of incorporating the username and password into the ASP script in order to overcome the problem! (after all, I CAN write files to the Uploads folder when I use ftp!)

I have an inkling that one way round it is to incorporate the passowrd and username into a log-in script, so that anyone who logs in will be able to upload but how is this done?

I assume this is a common concern and the answer is out there (surfing has not yet brought it to my shore!)