Not really. What I wanted to say (maybe I didn't find the appropriate words) is that I'm already contributing quite a lot of my time to Q2A. So when you ask me to help you, even if I hadn't answered your question or all the comments, I wanted to make it clear that I'm already helping you. So rather than asking for my help your asking for more of my help. That's fine, but it is up to me (and my schedule) if I will give even more.
Don't worry, I will. The answer to your extra help request is this:
1. Learn some Basic/Intermediate PHP (essential)
2. Learn this http://docs.question2answer.org/plugins
. Note I'm saying "learn" not just "read". That also means you'll have to spend many (MANY) hours reading and writing code, making tests, failing. But eventually you'll succeed. You could take a look at 'page' module and 'layer' in particular as those are most likely the ones you'll be needing.
3. Use the layer to configure the appropriate register links (it is better than the approach that I suggested in my answer, of course)
4. Use the page module to create a new login section that will ask whatever field you need
5. When submitting a form in the new page, submit it against the actual register page and load it with some hidden field
6. Go to the layer again and add some code that checks that if you are displaying the register page AND you DO NOT have the hidden field set it will redirect to your custom page
This is obviously not bullet proof as anyone could create a POST against the register page with the additional hidden field but is one of the easiest approach.
Additionally, you could just add some JS to the 'onclick' event of the 'Register' link that would display a popup and then redirect to the register page. You can do that from the layer or even adding the JS directly to the header of the Admin section.
I've just showed you the door(s) in quite a lot of detail. Your move now