Help:Highlight if top 80% cumulative percentage of a product has less than 3 customers

Hello all,

I have run into a bit of problem and hope someone would be able to help me out!

I'm not sure how to automate the following: To highlight if the top 80% cumulative value of a particular product e.g. A, B,C, D has lesser than 3 customers. In my attachment, the final results I'm trying to achieve are that in column F.

Thanks in advance!

Cheers,
Jon