Dividing vector into groups by another vector

Question

I have the following table (for example, the real table is 100 rows):
It has a group name column, n students in group, and score.

I would like to build a forth column of cluster, which will divide the groups into 10 decimils of approximatly equal size, while preserving the score. So if i have a total number of 80 students in all groups together, than I'll have 10 clusters which have about 8 students each one more or less. the top cluster will consist the groups with the highest grade. I hope it makes any sense. My problem is more an algorithmic one, I prefer to have a solution in excel/vba other than R just because I need a more dinamic solution. I tried to do it manually by sorting the groups by score, and then summing the n of students until i get a number close to the decimil of the total number of students, but maybe there is an algorithem more precise and less frustrating than that.

Thanks