Display parallelPeriod MeasureValue

[PNevill]

I have researched this for 2 days and no luck ... looking for help now.

I have a Dimension set (Departments) going down in a crosstab.  I have 10 weeks within a Year going across.
Along side the Department I want to show the Current Weeks (across members) Sales value.  No problem so far.
Right below I wish to show the same period 1 year ago just beneath the Current Week Values.  I cannot figure out the syntax for this (if possible at all).
Here is the format"
     (Net Sales)             Week 1    Week 2     Week 3     Week 4
Dept 1   Current Yr         565         453           612           712
             Previous Yr       
Dept 2   Current Yr         582         523           634           801
             Previous Yr

In the top crosstab corner is a default measure (Net Sales)  in the Current Year cell I use the following:

total ( currentMeasure within set periodsToDate ( [Sales].[Calendar].[Standard Time Hierarchy].[Fiscal Week] , currentMember ([Sales].[Calendar].[Standard Time Hierarchy] ) ) )

I tried various combinations with parallelPeriod but to no avail.   Help is greatly appreciated!