What are the steps for calculating a mean-sigma portfolio in excel?

Mean-Sigma Portfolio Proportion of SPY 50% Return SPY Return Portfolio Date 12/1/15 1/1/16 2/1/16 3/1/16 4/1/16 5/1/16 6/1/16 7/1/16 8/1/16 9/1/16 10/1/16 11/1/16 12/1/16 1/1/17 2/1/17 3/1/17 4/1/17 5/1/17 6/1/17 7/1/17 8/1/17 9/1/17 10/1/17 11/1/17 95.59% 95.51% 101.41% 102.33% 104.07% 103.90% 108.25% 108.38% 107.84% 106.50% 110.43% 112.00% 114.68% 119.19% 118.82% 120.52% 122.22% 122.40% 125.53% 125.89% 127.80% 131.46% 135.48% 136.42% Return BND 101.48% 102.12% 103.04% 103.44% 103.45% 105.53% 106.17% 105.84% 105.96% 104.97% 102.26% 102.34% 102.78% 103.19% 103.17% 103.97% 104.71% 104.76% 105.19% 106.31% 106.03% 106.01% 106.02% 106.19%