I have completed a very complex Excel spreadsheet with a lot of equations, except ...

I forgot to include September

I have Jan through Dec, all the months, except the calculations for September. Of course all

the equations are currently perfect for the data that's here.

How do I add a whole new column without ruining the previous equations?

PS: tomorrow is my holidays and I have to go to work to finish this table, so bad.

would really appreciate some kind expertise :)