How to add mathematical function ??

[#1]

I have sales of 12 months but in different columns and I want to add them all in a column as Month and also wants to perform the sum of sales of that. So how can I perform ??

This is current data and wants to make chart as like this :-

[MarcoWedel]

If you don't explain why crosstable load is no option for you, we possibly won't be able to help...