Parent/Child/Grandchild Portal and filtering the grandchildren help needed

Database setup (relevant fields)

Client  (parent)
- client ID
- g_Selected Date (global field to pass date to another layout)

Department (child; many depts linked to one client)
- dept ID
- client ID (linked to client table)

KPI  (grandchild; many KPIs to one department, one for each date)
- dept ID
- KPI date
- KPI 1
- KPI 2

I setup a layout (based on client table) with a portal (based on department table).  The fields in the portal are the four listed in the KPI table.

The Problem:  How do I limit the portal to only show KPIs with a date based on a variable passed to the layout (actually, the global field in the Client table)?  I've tried to use the Filter option in the portal using the following calculation:

KPI::KPI Date = Client::g_Selected_Date

The filter will not display anything.  If I turn the filter off, I see all the KPIs (all days) for all the departments under that client ID.

Not sure how to limit the portal.

Reminder - the portal is based on the Department table, not the KPI table.  I think that is the problem.  The filter I want to do is to limit entries from the KPI table, but the portal is based on the Department table.

Example Entries in KPI table:

Record 1
DeptID:  1
KPI Date:  12/20
KPI1:  5

Record 2
DeptID:  2
KPI Date:  12/20
KPI1:  9

Record 3
DeptID:  1
KPI Date:  12/22
KPI1:  7

Record 4
DeptID:  2
KPI Date:  12/22
KPI1:  5

So, lets say that I have the date set to 12/22.  I only want to see records 3 and 4.  Without the filter, only the first two records appear no matter how many are in the KPI table.