How do I count trio in excel?

Originally Posted by Ron Coderre

The problem in the workbook you attached is that you changed the comma before the last ROW function into a plus-sign:
This: +ROW($A$1:$A$21)-1)=3))
Should be this: ,ROW($A$1:$A$21)-1)=3))

Mr. Ron,

I changed the command as you mentioned but it returns me the same error that the picture attached in the second message in our conversations

Can you do this command in the attachment that I sent and make available on the site? So I will understand what I missed.

Rafael