Formula Help

I would like to make a new field in Accounts using a formula. How can I make a formula that would look like this:

If "Account Owner" equals Account Owner 1 then "New Field" equals "Gross Commission" * .80

If "Account Owner" equals Account Owner 2 then "New Field" equals "Gross Commission" * .30

If "Account Owner" equals Account Owner 3 then "New Field" equals "Gross Commission" * .20