Counts of item categories in summary field

[Matthew F]

This is not such a rare situation, but I'm puzzled, about how to list the count of related records in a summary part.  The setup is like this:  

 

I have a table of "Boxes" that is related to a child table of "Items" via the key field pk_box. However, boxes are also grouped by box color (say red, green, blue, etc.).  

 

On a layout of item records, I have placed sub-summary parts that appears when records are sorted by color and pk_box.  On this summary part, a summary or calculated field can display the number of items in the found set for each box color.

 

What puzzles me, is how to calculate the number of boxes of a particular color and list this in the summary part?  A calculation using the count() function and a self-join relationship just give the total number of boxes of a particular color, but not the number in the current found set.  

 

>>  See attached example. <<

 

Thanks. 

boxSample.fmp12.zip

[comment]

See if this helps:

http://fmforums.com/forum/topic/61158-number-of-employees-from-payroll-report/#entry289204