Hi Rick,
1. If the week attribute is in yyyy-ww format, we can use datepart() for [This Week]:
with member [Transaction Date].[Week].[This Week] as
StrToMember("[Transaction Date].[Week].&[" + cstr(datepart("yyyy",now())) +
"-" + right("0"+cstr(datepart("ww",now())),2) + "]")
select [Transaction Date].[Week].[This Week] on rows,
[Measures].[Amount] on columns
from [Cube];
2. It's member not set. The member definition is between "as" and "select".
Ref: