@Chaosprinzip I think you could employ a counter and produce a rank and then get the thresholds for high, mid and low.
My problem is that it seems the case is not well defined. Are we talking about a rank or would the 60% be from the total amount of the value column? Maybe you could explain that further.
Here is a quick and dirty approach to use a Counter to create a relative Rank and automatically determine the threshold of the NGR column. But I think it needs a more clear definition from your side:
