I wanted to create a summary field on top of the summary field

I have report Detail section has been Hided, showing only Summaries on group footer section.

Jan_Amt              Feb_Amt             March_Amt        Apr_Amt…..until December

100         200         600         400

I wanted to sum all Summary fields from Jan_Amt to  Dec_Amt and display at the end of the row (in the same sectin)

Jan_Amt              Feb_Amt             March_Amt        Apr_Amt…..untile December     Total

100         200         600                         400     ..                                 1300

Basically I wanted to create a annual totals on the same row. Can we create a formula and use existing summary fields?.

I don't see that we cann add sum field in formula fields.

I am kind of new need help step by step process.

Thanks in Advance

-NB