Month&IF&Calculation

I would like to do calucation in field A1 that would use number that would change according to the month.
I am probably looking for an "IF statement".
E.G.
January = 8%
February = 17%
March = 2%
Result for January in A1 is 112 and the calculation goes like:
8% * 1398 = 112
For February goes like:
17% * 1398 with the result of 28 in the field A1
And for March goes like:
2% * 1398 = 28

So I would like to use the same field A1 and use different percentage automatically every month for calculation.
Thank you.
Kristina