Show two prices for each item

Let me first explain my store...

My store (http://www.livingtowers.com/coopstore) is essentially a store for members of our organic co-op to pre-order their produce for pick up on a Tuesday. No purchases or payments are actually made online. I would like to be able to put the member prices and non-member prices for each item on the site. As I said already, this isn't for people to pay online but just so they can see the savings they are getting by becoming a member. The non member prices are a flat percentage above the member prices. Is there a module or setting in the admin console that will allow me to do this?

Is the difference between Non-Member prices and Member prices a constant value? Or is it different for each Product?

It's different for each product and the price itself usually changes each week.

You might look to see if you can adapt this MSRP Display add on to what you need:
http://www.zen-cart.com/downloads.php?do=file&id=798