I am working on a medicine risk tool in excel.I am trying to make a stratification of my data by medicine risk levels and a randomization of cities by risk levels. I want the randomization to be proportional when it chooses the cities by risk level. 

```
Total.City.Region Risk Score    Total.City.Regionl.Risk.Desc    City.Scaled
4.43                                  1. Extremely Low Risk        0.129
443.32                                2. Very Low Risk             0.164
44.33                                 1. Extremely Low Risk        0.132
110.83                                2. Very Low Risk             0.137
221.66                                2. Very Low Risk             0.146
288.16                                2. Very Low Risk             0.151
376.82                                2. Very Low Risk             0.158
4.43                                  1. Extremely Low Risk        0.129
44.33                                 1. Extremely Low Risk        0.132
110.83                                2. Very Low Risk             0.137

```

This a part of my data. So each city has total city risk score and risk levels are based on the risk score. Then I scaled the scores to normalize it. Now I want to create a formula that stratifies my data by risk levels. (Extremely low risk, very low risk and low risk) and then pick random cities (fox ex 5 cities in total) from each level (first from extremely low risk then very low risk and then low risk) but I want this to be in a proportional way.

Any help or suggestion on how I can do this will be very helpful

Thank you so much in advance.