you cannot add such a calculated "row" in your pivot table.
see the pivot table as any other chart type and you'll get why
financial presentation of results in qlik is (in my opinion) not easy.
a way to achieve this is to create a pivot table with mutliple expressions (measures), that you will move from columns to row.
but this of course means you need to define everything. and that use of dimensions will be very limited.
the other way is to precalculate everything in your datamodel (again, will result in very little possible use of dimensions in your pivot/chart)
have a look at this extension: (bottom line: it requires a lot of data preparation); it will help you in some way