Thank you all so much for your solutions and for your explanations. I understand it now. I was able to use Tony's solution in a SharePoint List which works very well and Alkey's solution in an Excel spreadsheet as either SharePoint doesn't support some of the formulaic content or I made an error entering(:; I will try again soon. Alkey's solution also works perfectly in Excel.

I so appreciate all of your timely and clear responses; they will all be used in my project.

Thank you again and I will mark this as SOLVED.
Sharon