When you first open the formula. Click at the position in your table where you wish to insert the sum total of the cell values above. Position the cursor where you want to paste a formula.
Click in a cell that should contain the sum of the rows.
Next click Formula in Data group. This will display a Formula Dialog Box which will suggest a default formula which is SUM LEFT in our case. Click in a cell that should contain the sum of the rows. To reference the contents of a table cell type the cell references in the formula.