Access files from Server using vBulletin Attachment System

[nokian125]

I need some help. I have data in my Server. Those files are directory like:

www.example.com/download/xyz.zip

Files size ranges from 40 MB to 1 GB. All we need is to link them to vBulletin board as attachments. We need to share these files in Server.
We want to allow special user group who can access these files. So, can't share direct links in forum. As then all users get links by sharing with each other. We'll manage group permissions by ourself. Somebody just help us to make
A modification that can convert these files links to vBulletin script so we can apply policies on it. Like to allow specific group who can download these files.
Or
A script that can access password protected folder of Server and allow access of user if he's registered and belongs to specific group of our forum. Otherwise script should able to reject him.

Please help us in this, we are ready to pay for making this script. Waiting for your reply.

Thanks