summing values in a column largest first until i reach a certain value

Hey all,

I need help with a problem

I have 4 columns one named supplier, one named group, one named year, and one named %. I'm trying to make a new column to sum from the largest % until it reaches 80%, and name the values inculded in the sum to 80% to be named yes, and all those that aren't included be named no. But I wan't this filtered by group and year.

Heres an example of just one group and year,

Any help would be much appreciated, if you need anymore info let me know.

Thanks 

Nathan