Populating an array of strings

I'm sorry if this is elementary, but I'm having a surprisingly difficult time finding helpful articles about this.

My report is grouped something like this:

Branch

Item

For each branch, I need to determine whether or not a specific item has had an itemCode assigned to it. Each department has this item, but not all of them have an itemCode assigned to it. If not, a message needs to be displayed in the footer of the Branch section.

My idea is to have a suppressed section in the Item group that checks to see if it has the itemCode assigned. If not, a message would be added to an array and the array would display in the Branch footer. For the next Branch, the array would have to be reset again.

How is this handled in Crystal Reports XI?

Thanks.