Add a total to the invoice report that will take the total amount and the pending amount and automatically calculate the difference in percentage for each location

When I click on invoices and scroll down to the total, it shows the total amount and the pending balance for each month and the total for each location. I was hoping there would be a way to have the difference automatically calculated in percentage for each location, as well as one total for all location. This will allow better assistance for us to see how far we are from our budget on a daily basis for each month?