Repeat Region Relation to Differentiate Between Contexts

My company has one Windchill context for Libraries and one for Products.  I'd like to write a Repeat Region relation that would differentiate between contexts and populate a drawing's BOM accordingly.

For example, if the assembly member comes from the Products context, I'd like the asm.mbr.name set to a parameter.  If the assembly member comes from the Libraries context, I'd like the asm.mbr.name to be just that.

Something along the lines of...

IF

     asm.mbr.PTC_WM_LOCATION==/Products

          asm.mbr.name=A relation-driven parameter in the part

ELSE    

     asm.mbr.name

Does anyone have a suggestion for how to access the PTC_WM... parameters?