Combining Sales reports

Manager needs me to combine these two reports, 2013 and 2012, showing sales increase or decrease by part number, by customer#, by location. Then, if we sold something last year and not this year, it needs to be on the report showing a 100% decrease plus if we sold something this year and not last showing, it needs to be on the report showing a 100% increase.

Does anyone have any suggestions?

Thanks for your help.