Plot cumulative data in Excel

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http://superuser.com – Is it possible to plot data in excel without having to define the function of the data in an extra column? Think of this simplified example: There are two columns with numbers A and B. Is it possible to plot A, B and Sum(A+B) without having to create a column to pre-calculate the last one (eg: =SUM(A1:B1))? Plot using extra column What I want to achieve I want to avoid extra columns (only one in this example) and have this logic directly in the graph. The above illustration is not valid, excel displays an error similar to "this function is not valid for this context" (I use Greek Exc (HowTos)