SSRS category group issue

Hi all,

I have a dataset that produces the following results

Sales Sales LYKey

Single                           500€   200€1

Double                         100€400€2

Combination                 ......3

System4

Allnull

I would like to use my own custom category grouping where I have :

-Combination (single + double + combi)

-System

-All

I can use an expression iif(key = 1, 2 or 3),"combi", "system"... but this only works for 2 attributes. Is there any way I can make 3 category groups where I also have the "all" group which is just the sum of all?

Thanks!