Pivot table to show difference between column instead of sum (Urgent)

Hi, i am doing a report to show variance between 2 years. HOwever, my pivot table keep on summing the year 2 instead of minus. I tried to do it in value setting, but in vain. Anyone can help?

For example, using auxiliary columns and the YoY calculation field.

Can you teach me how u get the YoY column?

I'll try,
1. You must place the mouse cursor within the pivot table.
2. Then click the "Analysis" tab from the main menu,
3. Select the "Calculation field" from the drop-down menu.
4. Enter the title and continue the formula for this field, e.g. "2017-2016" and add.