Conditional formatting

Attached is a VBA solution. The colors are set for a store every time there is any change in the Units for that store. But I'm not sure how that would happen if they're hidden. I have a feeling that there are important details about your question that are left out.

What is the realistic number of stores can occur for each store name? This solution assumes the max is 97. The formula uses 99 so it sticks out.

Also I discourage the use of merged cells. It prevented me from copying formatting from one column to another, and can cause all kinds of other problems.