Retail/ Minimum Order= Wholesale, please help

OK, now I know there is a wholesale/retail plugin but it doesn't do what I need it to.

What I want to have is:

on each product page, have two fields (that will be filled in on the regular product page in admin);

one price for retail (for example: $17.00)
one price for wholesale (for example: $12.00)

When a customer adds the product to their cart, they won't choose a price, it will just get added. The cart will display (for example, one product in cart- $17.00/$12.00),

Now, here's what I need done.
At checkout, there will be a "wholesale threshold". For example, if the cart has more than $150 (a price determined in admin area) in it, the wholesale prices will be applied, and a message will appear on the checkout page, something you can customize in admin (like, "congratulations, you have qualiified for wholesale priceing). Now, if the cart has LESS than $150 (or whatever the determined wholesale threshold is), the retail prices will be applied. it will say something like "add $xxx.xx more to your cart to qualify for wholesale pricing". (or you can choose in admin something else or display nothing at all). I am willing to pay someone around $20 to get this add on made to these specs. of course, if someone would do it for free :hug:.

But i need something like this for a client soon, so please respond if anybody can help.
Thanks,
peace
-adam