On this page...
[login to view URL]
...there's an area that says "Three Monthly Payments of $99"
(try using this coupon as an example: SAVE30 ... and you can see what I mean)
I was thinking maybe the script could search for the presence of the code SAVE30 ... if it was present in the page then display $69.30, if it wasn't present display $99
Hope that all makes sense.
Sadly, for security reason I can't give you access to the page so I will need to add the script myself (it's in our cart system with credit card info etc.