a2 = cat, dog, mouse
a3 = cat, mouse
a4 = dog, mouse
a5 =dog
a6 =dog

if user selects "dog" the array cycles through the cells that contain dog and should add them to the array. so a2, a4, a5 should be added.
Is it a fixed value, that is "dog" only? If it is not and could be any combination of values, it will require a separate and long code.
I am off the site shortly and hopefully some one will help you.