In Excel 2013 I want to run a formula that does the following:
If cell A1 is equal to zero then B1 is multiplied by 10% and C1 is multiplied by 20%, and D1 multiplied by (1-0.2).
Assuming you have your data in columns A to D, you can type in the following formulae into columns E-G, which will be calculated from B, C and D respectively
[in E1] =if(A1=0, B1*1.1,[whatever you want to happen if A1 NOT 0, e.g. B1])
[in F1] =if(A1=0, C1*1.2, C1)
[in G1] =if(A1=0, D1*(1-0.2), D1)