help with mdx query

Hello there,

i got time Hierarchy : YearKey-->QuarterKey--->MonthKey

for the MonthKey (which is the key of the whole table) i got an attribute called "NetWorkDays" and this attribute is a text filed and it gives information regarding how many workdays there is for each MonthKey.

when the monthkey member is displayed i get a number
when other member is displayed i get an error (thats because the "networkdays" is an attribute of the monthkey".

i need  to create a member that will sum for each quarter and year the grand total of it's children

for instance,
jan-2011 : 21
feb-2011 : 20
mar-2011 : 20

therefor, 2011Q1 sholud be sum of 21+20+20

and year 2011 should be sum of all 4 quartes

can anyone help plz?

this is the query:

WITH 
 MEMBER [Measures].[NetworkDays] AS
STRTOVALUE([Times].[Hierarchy].currentmember.properties("Network Days"))


select [Measures].[NetworkDays] on columns ,
[Times].[Hierarchy].members on rows 

 
from [MyCube]

thanks