I am putting together a spreadsheet and I need to set up a rule or formula that will:
If cell (A1) equals 'FF' then cell (A2)'s value subtracts 100 in cell (A3), but if cell (A1) equals 'SD' then cell (A2)'s value adds 50 in cell (A3), but if cell (A1) equals 'REV' then cell (A2)'s value just stays the same in cell (A3).

I'm using rule in A3 =IF(A1="FF",A2-100,IF(A1="SD",A2+50,IF(A1="REV",A2,"")))

How can I add to this rule, so then if cell (B1) equals 'MS', then the entire rule is over-rided and 1908 is added to the value in (A2) in cell (A3).