Try a table calculation filter, such as LOOKUP(ATTR([Week]),0)
This will apply the filter after the running sum has been calculated.
Andrew is example right. This requires the use of a Table Calc filter (also sometimes referred to as a "late filter") to ensure that you retain all of the weeks required for your running total, while still only displaying the one week of interest.
Since I already created an example workbook in the meantime, I'll go ahead and attach it.
1. Add [Week Number] to the Rows (first pill). Turn off "Show Header".
2. Create a calculated field [Week table calc]. Configure it to calculate along [Week Number].
3. Make [Week table calc] discreet, and add it to the Filters shelf. Show the filter, configure it as a dropdown, and voila.
Sample workbook attached (version 10.1.4).
Accum Sales_JC-10.1.4.twbx 29.7 KB
Thank you very much Jamieson! It works perfectly. Well explained!
I only have to compute my totals using Week Number and that's ok.