A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
let' say you are including in your pivot table column M from the two database, then take one data base and for example column P enter this formula
=M2*-1
then copyformula down, this column will be negative now, in column P of the other database enter
=M2
now when you combine both within the Pivot table include column P instead of M and you will have the difference