Zend certified PHP/Magento developer

How to count unique text values in an Excel TABLE

I have found many options to count unique text values in an Excel column. But nothing on how to do it in a spreadsheet formatted as a table. The formulas I have seen so far counts all the rows regardless of the filtering. I want to be able to count only the rows resulting after I filter the table. To explain better, my table has over 100 rows; but only 27 unique values. The formula will always show 27 even when I filter data on another column. Any ideas?