Member property to be used in a set???

[deleted_user]

Hi there, I want to use member property to form a valid Set. Is it possible?
For example if I have a hierarchy
[TimeDimension].[Year].[Week]
and if I want to have a lookup for year and week, can I declare 2 member properties for comparison year and week?? say, prev week and prev year and use it in my set like this:-
[TimeDimension].[iif([TimeDim].currentmember.level is [TimeDim].[Week],
StrtoValue([TimeDim].currentmember.properties('Preyear')),0)].[iif([TimeDim].currentmember.level is [TimeDim].[Week],
StrtoValue([TimeDim].currentmember.properties('Prevweek')),0)]
So if current year is 2008 and I want to get data for a measure say Sales for 2007 for a period which is NOT like for like will this work???

Note: both member property has been assigned to level Week

[deleted_user]

Just to update this track. Example would be
[TimeDimension].[2007].[5] and if it retrieves any measure then

([TimeDimension].[2007].[5], measure1)