Can the following IF statement be shortened at all?

=IF(CO10<>0,IF(MONTH(O1)=1,O3,IF(MONTH(O1)=2,S3,IF(MONTH(O1)=3,W3,IF(MONTH(O1)=4,AA3,IF(MONTH(O1)=5,AE3,IF(MONTH(O1)=6,AI3,IF(MONTH(O1)=7,AM3,IF(MONTH(O1)=8,AQ3,IF(MONTH(O1)=9,AU3,IF(MONTH(O1)=10,AY3,IF(MONTH(O1)=11,BC3,IF(MONTH(O1)=12,BG3)))))))))))),IF(MONTH(O1)=1,O4,IF(MONTH(O1)=2,S4,IF(MONTH(O1)=3,W4,IF(MONTH(O1)=4,AA4,IF(MONTH(O1)=5,AE4,IF(MONTH(O1)=6,AI4,IF(MONTH(O1)=7,AM4,IF(MONTH(O1)=8,AQ4,IF(MONTH(O1)=9,AU4,IF(MONTH(O1)=10,AY4,IF(MONTH(O1)=11,BC4,IF(MONTH(O1)=12,BG4)))))))))))))

Depending on what month is in cell O1, it takes the value from O3 if O1=1, S3 if O1=2, W3 if O1=3 etc....

I'm looking to use this formula as part of a bigger one, so having this formula as small and as simple as possible would be a great help.

Any help/suggestions much appreciated.

Best regards

manc