M$ 2nd chance promotion booking

I've not book an exam online before. but from what I understand, if I were to register for M$ promotion exam, I will be given a code. At this point of time, I intend to purchase discount voucher off the web. And I will be issued a code too. Meaning that I'll have 2 codes in hand.
But I've seen that the prometric online booking contains a single textbox for entering voucher/discount code. Makes me confuse that which should I enter into the textbox.
Please advise.
But I've seen that the prometric online booking contains a single textbox for entering voucher/discount code. Makes me confuse that which should I enter into the textbox.
Please advise.

Comments
you could try phoning them, and ask them how to enter it on the website.
I've asked the test center but they told me to inquire from prometric as they are not sure either. Hopefully someone who is experienced can guide me along.
i'd say just do it like that if you're not sure.
http://www.microsoft.com/learning/mcp/offers/2ndchance/details/
Good luck with your exams.
MCP,MCSA,MCSE(Windows 2000)(210,215,216,217,218,219,220)
Aiming for MCSE 2003 by end of 2006
http://www.jc-hosting.co.uk/refer.php?id=techexams
Please correct me if my assumtion is incorrect.
The link two posts infront of yours states that your register your second chance (with MS) before booking an exam (use your discount coupon)... When you fail, you rebook and exam using that code MS provided you. You must wait a day or so for the failure to show up in their records and the "code" to become active.