There are several approaches possible depending on your version of filemaker and how you need to display this data.
An older method that is a bit complex to implement but which does the job in a summary report layout is to use the A new way to count unique values in FileMaker 12 method.
If you have a table of customer records with one record for each customer, you can count the related records in this table if you can set up a relationship that works. Sometimes this takes a Go to related reocrds with the match found set option followed by a get (foundCount) function to count the records on this other layout.
If you have FileMaker 12, you can use a SQL query in an Execute SQL function call to count your distinct values: A new way to count unique values in FileMaker 12
I will use the sum of the reciprocal since i only have FIlemaker 11, but i can not get your cFraction GetSummary to work.
I have the count, but the next step, i can't nail down.
SCount Summary - Count of CustomerID
SFraction Calculation 1/ GetSummary (SCount ; Customer ID)
the break field in a GetSummary function (Customer ID in the example) works just like the "when sorted by" field in a Sub Summary layout part. Your found set must be sorted by the break field to group records with identical values in this field or it will not return a value.
Thank you for clarifying Phil. This might be where my complication has been.
In my layout, i am sorting by a related field and the subsummary is based on that related field. So when i build my count field, i can not have it count a related field. And if i build the count field in my related table and add it to my layout, it doesn't add.
Please describe the design of your report and the structure of your data in detail.