Nested Pivot Table Header AKA Two Row Header Summary Report Needed

Anyone have suggestions on the how to create the following...

I'm needing to create a two-level summary report (aka Pivot table with two-header row).

For the report on the vertical, I'd like a Manager field.

...

For the horizontal, I'm needing to group (at the top) Week Number and then beneath it (Group Values) 

so that I can see  something like this...

+---------+-------------------+-------------------+-------------------+
|         | Week 1            | Week 2            | Week 3            |
+---------+-------------------+-------------------+-------------------+
| Manager | Group 1 | Group 2 | Group 1 | Group 2 | Group 1 | Group 2 |
+---------+---------+---------+---------+---------+---------+---------+
| Mgr1    | 12      | 3       | 0       | 4       | 6       | 8       |
+---------+---------+---------+---------+---------+---------+---------+
| Mgr2    | 3       | 0       | 0       | 10      | 8       | 11      |
+---------+---------+---------+---------+---------+---------+---------+