I currently have a website with a standard form that works as follows:
1) User enters info into form and submits.
2) Data gets added to DB
3) Page gets reloaded and user is informed that they have successfully joined.
4) SMS Message gets sent to user about how to verify registration.

I need it changed so it works like follows:
1) User enters info into form and submits.
2) SMS message is sent with a random generated PIN number.
3) Data is logged in DB, flag set as 'unconfirmed'.
4) DHTML popup appears over form area informing user that they need to complete registration by entering this PIN number on a form contained in the popup.
5) User enters correct PIN and DB entry is updated as 'registered', or shown PIN form again if they enter wrong PIN.

So essentially its changing the form from a normal submit type form to a DHTML popup, and the addition of a PIN (password) entry to confirm registration. All the code for eg SMS message sending is already written, so this is a minor task.


4) User enters their PIN