Once your table is ready, you can use aggregate functions on numeric values of your table structure. To use functions, carry out the following steps:
First add the totals of both columns in the 'Total' row.
Click column 2 of the last row and then the 'Layout' tab.
In the 'Formula' textbox, type '=SUM (ABOVE)'.
To view results, right-click the cell value and select 'Toggle Field Codes'.
Next, go to the first cell of the 'Difference' column.
Click the 'Formula' button appearing under the 'Data' group of 'Layout' tab of under the Table Tools'section.
Treating the table as a mini Excel sheet, change the formula in the 'Formula' text box and click 'OK'.