Criteria Based Group Members and a Multi-Valued Attribute

Currently, I"m managing group membership using a multi-valued database table.  That works well.  But, the logic for group membership resides on a DB server and requires a developer or a DBA to alter (along with a bunch of change control overhead).

In this instance, we have cases where an employee has duties in more than one building.  Those building lists are stored in the metaverse in a newly created multi-valued attriubte "building".  The MAs I have in place maintain that properly. 

I'm going through an effort to move that into the portal.  I have the groups and users created in the portal.  But, when I try to define the group as a criteria based group, the list of selectable attributes does not include "building". 

At first I thought the portal didn't support multi-valued string attributes.  But, I found instances in the default drop down that are multi-valued, non-indexed attributes.

Then, I thought the reason I wasn't seeing that attribute was because of some MPR.  So, I added the "building" attribute to these MPRs:
    Synchronization: Synchronization account controls group resources it synchronizes
    Group management: Group administrators can update group resources

My question is, what do I need to do to get my "building" attribute to show up in the criteria attribute selection drop down?  Or, is that not supported?  Or, am I missing something?

Thanks,

Greg