need advice on integrating PunBB with paypal/worldpay

Hi,

I am in the middle of developing a couple of subscription sites that will use pubBB for the forum.

I have got the basic site developed and ingrated the forum. It looks and works great. I have a seperate page with log in/out features etc.

I need some general advice on how to integrate the payment system, and the order of the steps.

From what I can see, I need the following steps:

1. Sign up form on my site which lets you choose username, email etc
2. transfer Worldpay/paypal where you enter credit card details etc
3. use the call back feature which can be customised to comfirm whether the subscription request was valid.
4. 'Approve' the new account in punbb, send email confirmation

My initial thought was to have a form which would store sign up details in temporary table. After this data was entered, go to paypal and pay, and then use a call back to activate a PHP script on my server to add the user to the forum. I would use the row number in the temporary table as a reference in the call back.

Any thoughts ?

Will