EXCEL adding new columns into nested if statement

=IF(Payment_Rules=Save_Only,IF(VLOOKUP(F7&$B$13,$Y$13:$AC$429,IF($Z$11=$B$6,2,IF($B$6=$AA$11,3,IF($B$6=$AB$11,4,5))),FALSE)<D6,D6,VLOOKUP(F7&$B$13,$Y$13:$AC$429,IF($Z$11=$B$6,2,IF($B$6=$AA$11,3,IF($B$6=$AB$11,4,5))),FALSE)),VLOOKUP(F7&$B$13,$Y$13:$AC$429,IF($Z$11=$B$6,2,IF($B$6=$AA$11,3,IF($B$6=$AB$11,4,5))),FALSE))

So far I have nested if statement in my excel file like this and it works fine, but new columns are added to the workbook so I have to tweak this code little bit to cover new columns.(column AC:AF are added)

=IF(Payment_Rules=Save_Only,IF(VLOOKUP(F6&$B$13,$Y$13:$AF$429,IF($Z$11=$B$6,2,IF($B$6=$AA$11,3,IF($B$6=$AB$11,4,IF($B$6=$AC$11,5,IF($B$6=$AD$11,6,IF($B$6=$AE$11,7,IF($B$6=$AF$11,8))))))),FALSE)<D5,D5,VLOOKUP(F6&$B$13,$Y$13:$AF$429,IF($Z$11=$B$6,2,IF($B$6=$AA$11,3,IF($B$6=$AB$11,4,IF($B$6=$AC$11,5,IF($B$6=$AD$11,6,IF($B$6=$AE$11,7,IF($B$6=$AF$11,8))))))),FALSE)),VLOOKUP(F6&$B$13,$Y$13:$AC$429,IF($Z$11=$B$6,2,IF($B$6=$AA$11,3,IF($B$6=$AB$11,4,IF($B$6=$AC$11,5,IF($B$6=$AD$11,6,IF($B$6=$AE$11,7,IF($B$6=$AF$11,8))))))),FALSE))

This is what I got for my new code, but it gives me the #REF! error. I can't figure it out what is wrong with. Since original code works fine I know there's nothing wrong with calling reference. How can I fix this error ?

Thank you!