Hi Richard,

I came to the same conclusion as your suggestion, however it still doesn't do the job.
=COUNTIF(C:C,"<="&C3) only counts windmills that are in "commissioning OR commercial operation" or "commercial operation". It doesnt distinguish if a wind mill is in commercial or commissioning before the given date the criteria is set to - hence the logic dictates that it counts windmills in commissioning and commercial operation as "in commissioning".... if you know what I mean? It's close, but no cigar.

It took me some time to see it, but look at it and you will see.

Note: I found it helpful to reduce the data to only contain around 10 windmills. Then you quickly see the problem that the formula doesnt fully know how to distinguish between "in commissioning" and "in commercial operation" as to absolute different values that are mutually exclusive.

This task is a pain in the b*tt!