distinct count of a filtered column

[Jay1395]

Hi,

I am trying to get a count of distinct values in a filtered column. I have it actually working, but each run it gives me a popup which says "Unknown". It runs fine after that is clicked but I am working what I have written to cause that.. I took a screen shot of my expression builder.

[orange]

With a function possibly based on

select count(YourField) as num_of_Something
from
(
    select distinct YourField from YourTable
)