prodigy-
What you are asking for is a custom script to interact with your site. It will register people who want to sign up, send them a welcome letter with a confirmation link, store all the users info in a database and then give them access to portions of your site- That is a very detailed process requiring an extensive knowledge of php and or Java script. To accomplish this you would have to hire someone to write that script for you.
You could do a google search and find a registration script, but again you would need the knowledge to modify it to suit your particular needs.
Naval (above),
Watdaflip and
David offer such services.
Please keep in mind that it is not an unwillingness to help you with your question, but that the magnatude of what it would take to accomplish is beyond the scope of this forum as a volunteer community of BV users trying to help and give simple advice.
Andy