excel should have a feature to count distinct data points in a row or column this feature is only available in advanced filter currently
While this isn’t a single function to do what you want, you can accomplish this today with the formulas outlined on the following page.
Hope that helps,
I know that there are ways to simulate a "DISTINCTCOUNT"-Function in the suport.office-description, but they are actually quite complex. Counting distinct values in a cell area is not that exotic or uncommon, there should be a simple formula to do that.