I have tried...without success.

A B C D
dog 1 brown 2
cat 1 brown
dog 2 black 4
cat 3 blue

For example: I need a formula that says if column D has a value in it AND
column A = "dog", then sum column B. I have tried versions of the SUMPRODUCT
function but cannot solve it. The problem is that column D cells contain a
formula, I think. Any help is greatly appreciated.