Cells B10:K10 contain sales data. Cells B20:K30 display the percentage of
Product A included in cells B10:K10.

To reduce clutter in B20:k30, I added data validation that only permits
entries if the corresponding row in B10:k10 contains numbers greater than
zero. The problem is that cells B20:K30 are used in subsequent
multiplications and, if they are left unpopulated as a result of data
validation restrictions, I end up with a bunch of #VALUE# errors. Is there a
work-around?