Ranking or Class Feature? Not sure how to use...

[#1]

I have the following Data set...

I'm try to determine the top 25% Customers...then the next groupd 26%-50%, then the next group 51% - 75%, etc...

Thanks for any help...

CRFamilyName	Sales	Relative
Customer 1	$6,690,606.38	31.95%
Customer 2	$1,943,962.70	9.28%
Customer 3	$1,334,360.11	6.37%
Customer 4	$1,253,137.48	5.98%
Customer 5	$936,765.36	4.47%
Customer 6	$916,117.25	4.38%
Customer 7	$873,306.49	4.17%
Customer 8	$649,852.43	3.10%
Customer 9	$632,122.42	3.02%
Customer 10	$595,284.03	2.84%
Customer 11	$580,841.47	2.77%
Customer 12	$561,855.07	2.68%
Customer 13	$504,677.42	2.41%
Customer 14	$476,079.26	2.27%
Customer 15	$460,443.05	2.20%
Customer 16	$431,254.32	2.06%
Customer 17	$382,649.13	1.83%
Customer 18	$351,853.39	1.68%
Customer 19	$347,480.14	1.66%
Customer 20	$344,520.21	1.65%
Customer 21	$340,241.84	1.62%
Customer 22	$331,368.63	1.58%