This very much possible in Qlikview, Taking your above mentioned example . Here you can implement new field called
Rowno( which will be having number like1,2,3......) From your above example you want to implement % t row number 2 & 4.
So here you can give a condition in expression that is :
In this case against rowno 2 and 4 you will be getting your numbers in % format.
This is sort of an extended P&L. I don't know how you'll manage to display the different P&L items, but usually an artificial dimension is created that lists the different P&L items to be displayed. Add a flag field to that list of items and set it to PERC when a percentage should be shown, and something else (or just nothing) when the regular value should be displayed.
Your expression will become somthing like:
=IF(PNLFlag = 'PERC', num(sum(Values) / sum(TOTAL NetSales), '##0%'), sum(Values))
Of course the expression itself may require some tuning as you didn't supply details about the actual data.