Simple script

Hi I need a very basic script made Here is what I need. Ability to have one clickupsell to membership (Using [login to view URL] or [login to view URL]) So here is a use case: customer buy my ebook for $17 then after sale they have the ability to be in my membership site for $27 per month (they just click on button, they don't have to enter their credit card again) if they dont' take the upsell for the $27 per month They get a downsell for something else which is just $10 per month So basically I need a script that has one upsell and one downlosell for membership and can make that a one click. I need this fast so pelase only bid if you have experience making something like this before. Please shoot me a message with a demo you have made if you have done this before. Thanks, Gary