move_uploaded_file

I have a file uploading function that works well on my local server. It finds a picture and uploads it into a defined directory. Unfortunately this function does not work when I try to upload to my web host. It says I do not have the proper permissions. I believe this has to do with the fact that my web host requires a user name and password for all file transfers for security reasons. I still want my users to be able to upload files or pictures to my web host (if I have granted them proper access through my log in). How do I indicate the correct login sequence for my web host with a function like "move_uploaded_file"? - Matt