Analysis Servicies Mdx

hello
I need help I need to create a single calculated member which allows add (accumulate) the securities months, quarters, semesters. but with the following sentence works for me is creating a separate calculated member for each one, all together if I get error if not using a CASE can do, I can INDICATE HOW CAN I USE THE CASE or some other function

CREATE MEMBER CURRENTCUBE.[MEASURES].[C_Mes]
AS SUM([TIEMPO].[BG TIE Mes].&[1]:[TIEMPO].[BG TIE Mes].CURRENTMEMBER,[Measures].[BG HEC Valor]),

SUM([TIEMPO].[BG TIE trimestre].&[1]:[TIEMPO].[BG TIE trimestre].CurrentMember,[Measures].[BG HEC Valor]),


SUM([TIEMPO].[BG TIE Semestre].&[1]:[TIEMPO].[BG TIE Semestre].CurrentMember,[Measures].[BG HEC Valor]),
FORMAT_STRING = "#,#",
VISIBLE = 1;

Have you taken a look at the following article here at Database Journal (a member of my MDX Essentials series)?

MDX Scripting Statements: Introducing the Simple CASE Statement

I give guidance in the use of the CASE statement therein that will help you meet your stated need, as I undertand it. Check it out, and get back if you have any further questions...

Good Luck!

Bill