|As stated here:|
"Iteration is a powerful feature in Excel, but not one that is familiar to a large number of users."
I, for one, am not at all familiar with using iteration in Excel.
That said, if I had to use it, I would Google 'Excel Iteration' and read some of the various articles on the subject. Many of them (including the one I quoted) have examples of how iteration can be used in a spreadsheet.
Perhaps a review of those articles will point you in the right direction.