Pricing by size after item selection

I am using ZenCart 1.3.8a and PHP 5.2.9
I want to allow the user to select an item, then choose a "size" (one of four possible sizes A, B, C, D). Price is determined by size.
I hope to not have to set up four separate products for each to do this. I want a pull-down that allows the user to change "size" which changes price at the same time. So when entering a product in admin I would be applying two or more price/size attribute pairs to each product.
I've searched the forums and the Web, can't find anything about this kind of feature. Anyone know how to make this happen, or know where instructions are?

https://www.zen-cart.com/tutorials/index.php?article=57

Thanks, I did see that article.
My problem is that the price per size is complicated, for each item I have up to four prices. So for example Item one will have size A priced at X, and size B priced at Y.
But Item two will have size A priced at M and size B priced at N.

So my problem is I can't just set up four pre-defined options like A/B/C/D across all products, I need to be able to define what the price is per option per product.

Hope that makes sense, and I hope there is a way to make this happen.

You'll have to set up different attributes for products with different colors/prices etc.

Does that mean I have to set up separate "Products" for Item 1/Price A and Item 1/Price B? That means they will both show up as part of the "category," so each Product shows up two or more times.

Perhaps your advice still applies, but I can't figure out how to set up and Attribute with up to four values, each value specific to the Product. I am definitely confused by the Attribute Manager page, but I can't figure out how to make this happen.

Total of about 40 Products, with 2 to 4 prices for each, total of about 80 to 160 different "Product/Size" pairs.