HELP! How to set up Specials for each attribute

I have a question in regards to setting Specials. We have a lot of products which are priced by attributes i.e. 1oz bottle = $4, 2oz bottle = $6, 4oz bottle = $9 etc.

We want to offer specials on a few products where each size is discounted not by a fixed amount, not by a percentage, but more arbitrary i.e. 1oz = $3, 2oz = $5 etc.

I can't figure out how to do this. If I input a special for the 1oz size, for example, it automatically reduces the amounts for all other sizes of this product. I DO want those reductions but not based on the reduction of the 1st size. Is that doable and how?

Zencart 1.3.8 user

Yolanda