MDX - Creating a dynamic grouping member?

Question

Category {A,B,C}

Value

Currently I can get:

Category    Value
--------    -----
A           100
B           200
C           300

What I'd like to get is:

Category    Value
--------    -----
A           100
B           200
C           300
D           500

Where D is the value of B + C.

Answer 1

Wow, this was actually incredibly easy...

with member [Category].[Name].[D] as
    [Category].[Name].[B] + [Category].[Name].[C]

select
    {[Measures].[Value]} on columns,
    [Category].[Name].allmembers on rows
from [Cube]

Result:

Category    Value
--------    -----
A           100
B           200
C           300
D           500