This is an interesting idea. Currently the action screen contains a checkbox in the email section for "All clients". Perhaps this can be highlighted somehow to indicate whether there are in fact multiple clients. There are probably other ways the action screen could be improved to indicate this also.

You could use the Priority Manager to update the summary of the job as mentioned. You would need to use the Custom SQL option in the Priority Manager definition to select jobs with multiple clients. You could use a statement like.

SELECT JobPKID FROM [qryRelationshipsClientLinkedToJobs_All_Count] Where NumberOfClientsLinkedToJob > 1

Then use the "Execute this SQL" on the action screen to update the job as you want. (test first on a backup!!!)

Would be interested in hearing other ideas on how this might be improved.

Hope this helps.
Rod