Conditional formating cells that add up to % of total

[Peter h]

Initial Weight	Sieve 1	Sieve 2	Sieve 3	Sieve 4	Sieve 5	Pan
100 g	2	15	20	25	15	23

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I would've googled this, but I'm not exactly sure how to word it. What I'd like to do is do conditional formatting for cells that add up to 90% of the total sum of cells in the range. Not sure how to approach this. Here is an example of my data.

I'm doing Sieve analysis at work, and want to be able to see at which point 90% of my sample is making it through the sieve. So, in my example table, the data for Sieve 2 would be the highlighted cell, because adding the data backwards starting with the "Pan" column, I don't add up to 90% until I add Sieve 2.

 

[Peter h]

I got it figured out. If anyone else is interested. In the conditional formatting putting the formula "=SUM(A2:$G2)>=$A1*.9" and it formats it exactly how I want it.