This requires a Log In script . There are some free on the net, and some paid for. You can Google it to find what suits you.
Within the lomits of the VodaHost family there are two solutions that allow users to setup their own password an username:
1.
http://www.dbtechnosystems.com/logginexamples.php for a custom made solution.
2.
http://www.vodahost.com/vodatalk/ser...in-script.html by Watdaflip.