Counting unique values within a FILTERED portal
I have figured out how to count the number of unique values within a particular field on records inside a portal. I use this to do things like, say, count the number of different source_property_names that appear within a "cluster" group of properties. This takes place by doing a calculation on the join table:
ValueCount ( ValueListItems ( Get ( FileName ) ; "names_calc") )
"names_calc" is a value list that uses the values from the source_property_name field.
So this works great for my current portal display layout. However, I would like to be able to display the information from the records inside the portal more granularly. For instance, there is a field named "source_property_performance", and that might be "H", "M", or "L". I can create a filtered portal that will only display records with one of those particular values just fine, and can easily do things like count the total number of records in a filtered portal and display that number. However what I want to do is count the number of unique "source_property_name" fields within a portal that is being filtered by the "source_property_performance" value. This currently does not work correctly, as far as I can tell.
Any ideas for successfully doing this? Again, long story short, it's "how do I count the number of unique values in a particular field of the records within a filtered portal?"