I need to build a formula to walk a column of comma-separated values and count the number of *unique values* seen. I am using Excel 2010. I have a screenshot of some example data...

The output of the formula in this case should be 5. In other words, the formula must count the following values: 2.3.0, 2.4.1, 2.4.2, 2.4.3, 2.4.4

I have figured out how I can simply count the raw number of comma-separated values like this...

=SUMPRODUCT(--(M123:M127<>""),LEN(M123:M127)-LEN(SUBSTITUTE(M123:M127,",",""))+1)

However, that formula yields `7`

, because it counts 2.4.3 and 2.4.4 twice.

I'm at a loss for how to reject repeated comma-separated values in different cells of the same column.

Due to the other systems that must interface with the spreadsheet, answers can only use a formula; they must not use VBA or some kind of filter.