We have products with different attrinbutes (sizes). 1L, 1.5L, 500mL, etc.

How can we just just one of the sizes onsale using the Specials functionality that exists in ZenCart??

Edit Products -> Zencart

Right now it only looks like we can select a product to put on special. But we would like to be able to put just one size of a product on special.

thanks!