Forum :: Lounge :: website gamertag system

Ive looked around google for along time now, and i can't find what im looking for.

Explanation:Ok, so picture a form on a website.  The form would look something like this;

 Gamertag: [___TEXTBOX_____]

  [GO]

.

Then once they press "GO" then it displays the gamertag below the form.  Yes its for my clan.  Then it removes the form for that PC using HDID or the computer name.  This way they can't spam it..?

Help would be most appreciated.